Configuration checks added

esbo_etc/classes/optical_component/AHotOpticalComponent.py

@@ -5,6 +5,7 @@ from abc import abstractmethod
 import astropy.units as u
 from astropy.modeling.models import BlackBody
 from typing import Union, Callable
+from ..Entry import Entry
 
 
 class AHotOpticalComponent(AOpticalComponent):
@@ -90,3 +91,21 @@ class AHotOpticalComponent(AOpticalComponent):
         """
         bb = BlackBody(temperature=temp, scale=em * u.W / (u.m ** 2 * u.nm * u.sr))
         return lambda wl: bb(wl)
+
+    @staticmethod
+    @abstractmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        pass

esbo_etc/classes/optical_component/AOpticalComponent.py

@@ -6,6 +6,7 @@ import astropy.units as u
 from astropy.modeling.models import BlackBody
 from typing import Union, Callable, Tuple
 from logging import info, debug
+from ..Entry import Entry
 
 
 class AOpticalComponent(IRadiant):
@@ -122,3 +123,21 @@ class AOpticalComponent(IRadiant):
             return self.__noise
         except AttributeError:
             error("noise not given. Method ownNoise() needs to be implemented.")
+
+    @staticmethod
+    @abstractmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        pass

esbo_etc/classes/optical_component/Atmosphere.py

@@ -1,7 +1,9 @@
 from .AOpticalComponent import AOpticalComponent
 from ..IRadiant import IRadiant
 from ..SpectralQty import SpectralQty
+from ..Entry import Entry
 import astropy.units as u
+from typing import Union
 
 
 class Atmosphere(AOpticalComponent):
@@ -37,3 +39,26 @@ class Atmosphere(AOpticalComponent):
                                                  qty_unit_default=u.W / (u.m ** 2 * u.nm * u.sr))
             # Initialize the super class
             super().__init__(parent, transmittance_sqty, emission_sqty)
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        mes = conf.check_file("transmittance")
+        if mes is not None:
+            return mes
+        if hasattr(conf, "emission"):
+            mes = conf.check_file("emission")
+            if mes is not None:
+                return mes

esbo_etc/classes/optical_component/BeamSplitter.py

@@ -1,6 +1,7 @@
 from .AHotOpticalComponent import AHotOpticalComponent
 from ..SpectralQty import SpectralQty
 from ..IRadiant import IRadiant
+from ..Entry import Entry
 from astropy import units as u
 from typing import Union
 
@@ -10,9 +11,9 @@ class BeamSplitter(AHotOpticalComponent):
     A class to model the optical characteristics of a beam splitter.
     """
     @u.quantity_input(temp=[u.Kelvin, u.Celsius], obstructor_temp=[u.Kelvin, u.Celsius])
-    def __init__(self, parent: IRadiant, transmittance: str,
+    def __init__(self, parent: IRadiant, transmittance: str, emissivity: Union[str, float] = 1,
-                 emissivity: Union[int, float, str] = 1, temp: u.Quantity = 0 * u.K,
+                 temp: u.Quantity = 0 * u.K, obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K,
-                 obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K, obstructor_emissivity: float = 1):
+                 obstructor_emissivity: float = 1):
         """
         Instantiate a new beam splitter model
 
@@ -22,7 +23,7 @@ class BeamSplitter(AHotOpticalComponent):
             The parent element of the optical component from which the electromagnetic radiation is received.
         transmittance : str
             The spectral transmittance coefficients of the filter.
-        emissivity : Union[int, float, str]
+        emissivity : Union[str, u.Quantity]
             The spectral emissivity coefficient for the optical surface.
         temp: Quantity in Kelvin / Celsius
             Temperature of the optical component
@@ -54,3 +55,44 @@ class BeamSplitter(AHotOpticalComponent):
             Manipulated incoming radiation
         """
         return rad * self._transmittance
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        mes = conf.check_file("transmittance")
+        if mes is not None:
+            return mes
+        if hasattr(conf, "emissivity"):
+            mes = conf.check_file("emissivity")
+            if mes is not None:
+                mes = conf.check_float("emissivity")
+                if mes is not None:
+                    return mes
+        if hasattr(conf, "temp"):
+            mes = conf.check_quantity("temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstruction"):
+            mes = conf.check_float("obstruction")
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_temp"):
+            mes = conf.check_quantity("obstructor_temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_emissivity"):
+            mes = conf.check_float("obstructor_emissivity")
+            if mes is not None:
+                return mes

esbo_etc/classes/optical_component/Filter.py

@@ -2,6 +2,7 @@ from .AHotOpticalComponent import AHotOpticalComponent
 from ..SpectralQty import SpectralQty
 from ..IRadiant import IRadiant
 from ...lib.helpers import error
+from ..Entry import Entry
 from astropy import units as u
 from typing import Union, Callable
 import numpy as np
@@ -22,8 +23,8 @@ class Filter(AHotOpticalComponent):
 
     @u.quantity_input(temp=[u.Kelvin, u.Celsius], obstructor_temp=[u.Kelvin, u.Celsius])
     def __init__(self, parent: IRadiant, transmittance: Union[SpectralQty, Callable[[u.Quantity], u.Quantity]],
-                 emissivity: Union[int, float, str] = 1, temp: u.Quantity = 0 * u.K,
+                 emissivity: Union[str, float] = 1, temp: u.Quantity = 0 * u.K, obstruction: float = 0,
-                 obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K, obstructor_emissivity: float = 1):
+                 obstructor_temp: u.Quantity = 0 * u.K, obstructor_emissivity: float = 1):
         """
         Instantiate a new filter model
 
@@ -33,7 +34,7 @@ class Filter(AHotOpticalComponent):
             The parent element of the optical component from which the electromagnetic radiation is received.
         transmittance : Union[SpectralQty, Callable]
             The spectral transmittance coefficients of the filter.
-        emissivity : Union[str, int, float]
+        emissivity : Union[str, float]
             The spectral emissivity coefficient for the optical surface.
         temp: Quantity in Kelvin / Celsius
             Temperature of the optical component
@@ -52,8 +53,8 @@ class Filter(AHotOpticalComponent):
 
     @classmethod
     # @u.quantity_input(temp=[u.Kelvin, u.Celsius], obstructor_temp=[u.Kelvin, u.Celsius])
-    def fromBand(cls, parent: IRadiant, band: str, emissivity: Union[str, int, float] = 1,
+    def fromBand(cls, parent: IRadiant, band: str, emissivity: Union[str, float] = 1, temp: u.Quantity = 0 * u.K,
-                 temp: u.Quantity = 0 * u.K, obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K,
+                 obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K,
                  obstructor_emissivity: float = 1) -> "Filter":
         """
         Instantiate a new filter model from a spectral band. The filter will be modelled as bandpass filter of
@@ -65,7 +66,7 @@ class Filter(AHotOpticalComponent):
             The parent element of the optical component from which the electromagnetic radiation is received.
         band : str
             The spectral band of the filter. Can be one of [U, B, V, R, I, J, H, K].
-        emissivity : Union[str, int, float]
+        emissivity : Union[str, float]
             The spectral emissivity coefficient for the optical surface.
         temp: Quantity in Kelvin / Celsius
             Temperature of the optical component
@@ -92,7 +93,7 @@ class Filter(AHotOpticalComponent):
 
     @classmethod
     # @u.quantity_input(temp=[u.Kelvin, u.Celsius], obstructor_temp=[u.Kelvin, u.Celsius])
-    def fromFile(cls, parent: IRadiant, transmittance: str, emissivity: Union[str, int, float] = 1,
+    def fromFile(cls, parent: IRadiant, transmittance: str, emissivity: Union[str, float] = 1,
                  temp: u.Quantity = 0 * u.K, obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K,
                  obstructor_emissivity: float = 1) -> "Filter":
         """
@@ -105,7 +106,7 @@ class Filter(AHotOpticalComponent):
         transmittance : str
             Path to the file containing the spectral transmittance-coefficients of the filter element.
             The format of the file will be guessed by `astropy.io.ascii.read()`.
-        emissivity : Union[str, int, float]
+        emissivity : Union[str, float]
             The spectral emissivity coefficient for the optical surface.
         temp: Quantity in Kelvin / Celsius
             Temperature of the optical component
@@ -129,9 +130,9 @@ class Filter(AHotOpticalComponent):
 
     @classmethod
     # @u.quantity_input(start="length", end="length", temp=[u.Kelvin, u.Celsius], obstructor_temp=[u.Kelvin, u.Celsius])
-    def fromRange(cls, parent: IRadiant, start: u.Quantity, end: u.Quantity,
+    def fromRange(cls, parent: IRadiant, start: u.Quantity, end: u.Quantity, emissivity: Union[str, float] = 1,
-                  emissivity: Union[str, int, float] = 1, temp: u.Quantity = 0 * u.K, obstruction: float = 0,
+                  temp: u.Quantity = 0 * u.K, obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K,
-                  obstructor_temp: u.Quantity = 0 * u.K, obstructor_emissivity: float = 1) -> "Filter":
+                  obstructor_emissivity: float = 1) -> "Filter":
         """
         Instantiate a new filter model from a spectral range. The filter will be modelled as bandpass filter of
         infinite order and therefore similar to a hat-function.
@@ -144,7 +145,7 @@ class Filter(AHotOpticalComponent):
             Start wavelength of the pass-band
         end : length-quantity
             End wavelength of the pass-band
-        emissivity : Union[str, int, float]
+        emissivity : Union[str, float]
             The spectral emissivity coefficient for the optical surface.
         temp: Quantity in Kelvin / Celsius
             Temperature of the optical component
@@ -202,3 +203,54 @@ class Filter(AHotOpticalComponent):
         """
         return lambda wl: np.logical_and(np.greater_equal(wl, start), np.greater_equal(end, wl)).astype(int) *\
             u.dimensionless_unscaled
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        if hasattr(conf, "band"):
+            mes = conf.check_selection("band", ["U", "B", "V", "R", "I", "J", "H", "K", "L", "M", "N"])
+        elif hasattr(conf, "transmittance"):
+            mes = conf.check_file("transmittance")
+        elif hasattr(conf, "start") and hasattr(conf, "end"):
+            mes = conf.check_quantity("start", u.m)
+            if mes is not None:
+                return mes
+            mes = conf.check_quantity("end", u.m)
+        else:
+            mes = "Expected one of 'band' / 'transmittance' / 'start' & 'end'."
+        if mes is not None:
+            return mes
+        if hasattr(conf, "emissivity"):
+            mes = conf.check_file("emissivity")
+            if mes is not None:
+                mes = conf.check_float("emissivity")
+                if mes is not None:
+                    return mes
+        if hasattr(conf, "temp"):
+            mes = conf.check_quantity("temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstruction"):
+            mes = conf.check_float("obstruction")
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_temp"):
+            mes = conf.check_quantity("obstructor_temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_emissivity"):
+            mes = conf.check_float("obstructor_emissivity")
+            if mes is not None:
+                return mes

esbo_etc/classes/optical_component/Lens.py

@@ -1,6 +1,7 @@
 from .AHotOpticalComponent import AHotOpticalComponent
 from ..SpectralQty import SpectralQty
 from ..IRadiant import IRadiant
+from ..Entry import Entry
 from astropy import units as u
 from typing import Union
 
@@ -10,9 +11,9 @@ class Lens(AHotOpticalComponent):
     A class to model the optical characteristics of a lens.
     """
     @u.quantity_input(temp=[u.Kelvin, u.Celsius], obstructor_temp=[u.Kelvin, u.Celsius])
-    def __init__(self, parent: IRadiant, transmittance: str,
+    def __init__(self, parent: IRadiant, transmittance: str, emissivity: Union[str, float] = 1,
-                 emissivity: Union[int, float, str] = 1, temp: u.Quantity = 0 * u.K,
+                 temp: u.Quantity = 0 * u.K, obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K,
-                 obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K, obstructor_emissivity: float = 1):
+                 obstructor_emissivity: float = 1):
         """
         Instantiate a new lens model
 
@@ -22,7 +23,7 @@ class Lens(AHotOpticalComponent):
             The parent element of the optical component from which the electromagnetic radiation is received.
         transmittance : str
             The spectral transmittance coefficients of the filter.
-        emissivity : Union[int, float, str]
+        emissivity : Union[str, float]
             The spectral emissivity coefficient for the optical surface.
         temp: Quantity in Kelvin / Celsius
             Temperature of the optical component
@@ -54,3 +55,44 @@ class Lens(AHotOpticalComponent):
             Manipulated incoming radiation
         """
         return rad * self._transmittance
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        mes = conf.check_file("transmittance")
+        if mes is not None:
+            return mes
+        if hasattr(conf, "emissivity"):
+            mes = conf.check_file("emissivity")
+            if mes is not None:
+                mes = conf.check_float("emissivity")
+                if mes is not None:
+                    return mes
+        if hasattr(conf, "temp"):
+            mes = conf.check_quantity("temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstruction"):
+            mes = conf.check_float("obstruction")
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_temp"):
+            mes = conf.check_quantity("obstructor_temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_emissivity"):
+            mes = conf.check_float("obstructor_emissivity")
+            if mes is not None:
+                return mes

esbo_etc/classes/optical_component/Mirror.py

@@ -1,6 +1,7 @@
 from .AHotOpticalComponent import AHotOpticalComponent
 from ..SpectralQty import SpectralQty
 from ..IRadiant import IRadiant
+from ..Entry import Entry
 from astropy import units as u
 from typing import Union
 
@@ -10,9 +11,9 @@ class Mirror(AHotOpticalComponent):
     A class to model the optical characteristics of a mirror.
     """
     @u.quantity_input(temp=[u.Kelvin, u.Celsius], obstructor_temp=[u.Kelvin, u.Celsius])
-    def __init__(self, parent: IRadiant, reflectance: str,
+    def __init__(self, parent: IRadiant, reflectance: str, emissivity: Union[str, float] = 1,
-                 emissivity: Union[int, float, str] = 1, temp: u.Quantity = 0 * u.K,
+                 temp: u.Quantity = 0 * u.K, obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K,
-                 obstruction: float = 0, obstructor_temp: u.Quantity = 0 * u.K, obstructor_emissivity: float = 1):
+                 obstructor_emissivity: float = 1):
         """
         Instantiate a new mirror model
 
@@ -22,7 +23,7 @@ class Mirror(AHotOpticalComponent):
             The parent element of the optical component from which the electromagnetic radiation is received.
         reflectance : str
             The spectral transmittance coefficients of the filter.
-        emissivity : Union[int, float, str]
+        emissivity : Union[str, float]
             The spectral emissivity coefficient for the optical surface.
         temp: Quantity in Kelvin / Celsius
             Temperature of the optical component
@@ -54,3 +55,44 @@ class Mirror(AHotOpticalComponent):
             Manipulated incoming radiation
         """
         return rad * self._reflectance
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        mes = conf.check_file("reflectance")
+        if mes is not None:
+            return mes
+        if hasattr(conf, "emissivity"):
+            mes = conf.check_file("emissivity")
+            if mes is not None:
+                mes = conf.check_float("emissivity")
+                if mes is not None:
+                    return mes
+        if hasattr(conf, "temp"):
+            mes = conf.check_quantity("temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstruction"):
+            mes = conf.check_float("obstruction")
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_temp"):
+            mes = conf.check_quantity("obstructor_temp", u.K)
+            if mes is not None:
+                return mes
+        if hasattr(conf, "obstructor_emissivity"):
+            mes = conf.check_float("obstructor_emissivity")
+            if mes is not None:
+                return mes

esbo_etc/classes/optical_component/StrayLight.py

@@ -1,7 +1,9 @@
 from .AOpticalComponent import AOpticalComponent
 from ..IRadiant import IRadiant
 from ..SpectralQty import SpectralQty
+from ..Entry import Entry
 import astropy.units as u
+from typing import Union
 
 
 class StrayLight(AOpticalComponent):
@@ -27,3 +29,22 @@ class StrayLight(AOpticalComponent):
                                              qty_unit_default=u.W / (u.m ** 2 * u.nm * u.sr))
         # Initialize the super class
         super().__init__(parent, 1.0, emission_sqty)
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        mes = conf.check_file("emission")
+        if mes is not None:
+            return mes

esbo_etc/classes/sensor/ASensor.py

@@ -1,6 +1,8 @@
 from ..IRadiant import IRadiant
 import astropy.units as u
 from abc import abstractmethod
+from ..Entry import Entry
+from typing import Union
 
 
 class ASensor:
@@ -52,3 +54,20 @@ class ASensor:
             The necessary exposure time in seconds.
         """
         pass
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was succesful.
+        """
+        pass

esbo_etc/classes/target/ATarget.py

@@ -5,6 +5,7 @@ import astropy.units as u
 import numpy as np
 from logging import info, debug
 from typing import Tuple
+from ..Entry import Entry
 
 
 class ATarget(IRadiant):
@@ -59,3 +60,21 @@ class ATarget(IRadiant):
         info("Calculating Signal for class '" + self.__class__.__name__ + "'.")
         debug(self.__sfd)
         return self.__sfd, self.__size
+
+    @staticmethod
+    @abstractmethod
+    def check_config(conf: Entry) -> bool:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        pass

esbo_etc/classes/target/BlackBodyTarget.py

@@ -3,6 +3,8 @@ from ..SpectralQty import SpectralQty
 import astropy.units as u
 from astropy.modeling.models import BlackBody
 from ...lib.helpers import error
+from ..Entry import Entry
+from typing import Union
 
 
 class BlackBodyTarget(ATarget):
@@ -44,16 +46,44 @@ class BlackBodyTarget(ATarget):
         Returns
         -------
         """
-        if band not in self._band.keys():
+        if band.upper() not in self._band.keys():
             error("Band has to be one of '[" + ", ".join(list(self._band.keys())) + "]'")
         # Create blackbody model with given temperature
         bb = BlackBody(temperature=temp, scale=1 * u.W / (u.m ** 2 * u.nm * u.sr))
 
         # Calculate the correction factor for a star of 0th magnitude using the spectral flux density
         # for the central wavelength of the given band
-        factor = self._band[band]["sfd"] / (bb(self._band[band]["wl"]) * u.sr) * u.sr
+        factor = self._band[band.upper()]["sfd"] / (bb(self._band[band.upper()]["wl"]) * u.sr) * u.sr
         # Calculate spectral flux density for the given wavelengths and scale it for a star of the given magnitude
         sfd = bb(wl_bins) * factor * 10 ** (- 2 / 5 * mag / u.mag)
 
         # Initialize super class
         super().__init__(SpectralQty(wl_bins, sfd), wl_bins, size)
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        mes = conf.check_quantity("temp", u.K)
+        if mes is not None:
+            return mes
+        mes = conf.check_quantity("mag", u.mag)
+        if mes is not None:
+            return mes
+        mes = conf.check_selection("band", ["U", "B", "V", "R", "I", "J", "H", "K", "L", "M", "N"])
+        if mes is not None:
+            return mes
+        mes = conf.check_selection("size", ["point", "extended"])
+        if mes is not None:
+            return mes

esbo_etc/classes/target/FileTarget.py

@@ -1,6 +1,9 @@
 from ..target.ATarget import ATarget
 from ..SpectralQty import SpectralQty
 import astropy.units as u
+from ..Entry import Entry
+from typing import Union
+import os.path
 
 
 class FileTarget(ATarget):
@@ -29,3 +32,28 @@ class FileTarget(ATarget):
         sfd = SpectralQty.fromFile(file, u.nm, u.W / (u.m ** 2 * u.nm))
         # Initialize the super class
         super().__init__(sfd, wl_bins, size)
+
+    @staticmethod
+    def check_config(conf: Entry) -> Union[None, str]:
+        """
+        Check the configuration for this class
+
+        Parameters
+        ----------
+        conf : Entry
+            The configuration entry to be checked.
+
+        Returns
+        -------
+        mes : Union[None, str]
+            The error message of the check. This will be None if the check was successful.
+        """
+        mes = conf.check_file("file")
+        if mes is not None:
+            return mes
+        mes = conf.check_quantity("wl_bins", u.m)
+        if mes is not None:
+            return mes
+        mes = conf.check_selection("size", ["point", "extended"])
+        if mes is not None:
+            return mes