class_docstr: Class implementing the EPS-SG-A1 MWS L1b Filehandler.
  
  This class implements the European Polar System Second Generation (EPS-SG)
  Microwave Sounder (MWS) Level-1b NetCDF reader.  It is designed to be used
  through the :class:`~satpy.Scene` class using the :mod:`~satpy.Scene.load`
  method with the reader ``"mws_l1b_nc"``.
class_docstr_tok: ["Class","implementing","the","EPS-SG-A1","MWS","L1b","Filehandler",".","This","class","implements","the","European","Polar","System","Second","Generation","(","EPS-SG",")","Microwave","Sounder","(","MWS",")","Level-1b","NetCDF","reader",".","It","is","designed","to","be","used","through","the",":","class",":","`","~satpy.Scene","`","class","using","the",":","mod",":","`","~satpy.Scene.load","`","method","with","the","reader","``","``","mws_l1b_nc","''","``","."]
docstr: Get the auxiliary data arrays using the index map.
docstr_tok: ["Get","the","auxiliary","data","arrays","using","the","index","map","."]
code: def _get_dataset_aux_data(self, dsname):
      """Get the auxiliary data arrays using the index map."""
      # Geolocation and navigation data:
      if dsname in [
          "mws_lat",
          "mws_lon",
          "solar_azimuth",
          "solar_zenith",
          "satellite_azimuth",
          "satellite_zenith",
          "surface_type",
          "terrain_elevation",
      ]:
          var_key = AUX_DATA.get(dsname)
      else:
          raise NotImplementedError(
              f"Dataset {dsname!r} not supported!"
          )
  
      try:
          variable = self[var_key]
      except KeyError:
          logger.exception(
              "Could not find key %s in NetCDF file, no valid Dataset created",
              var_key,
          )
          raise
  
      # Scale the data:
      if (
          "scale_factor" in variable.attrs
          and "add_offset" in variable.attrs
      ):
          missing_value = variable.attrs["missing_value"]
          variable.data = da.where(
              variable.data == missing_value,
              np.nan,
              variable.data * variable.attrs["scale_factor"]
              + variable.attrs["add_offset"],
          )
  
      return variable
  
imports: import logging
  from datetime import datetime
  import dask.array
  import numpy
  from netCDF4 import default_fillvals
  from .netcdf_utils import NetCDF4FileHandler
label_desc: Use image node_id 15 for calling the MWSL1BFile obj's underlying member method code with example usage: obj._get_dataset_aux_data(dsname) and returns: variable