class_docstr: Class implementing the MTG FCI L1c Filehandler.
  
  This class implements the Meteosat Third Generation (MTG) Flexible
  Combined Imager (FCI) Level-1c NetCDF reader.
  It is designed to be used through the :class:`~satpy.Scene`
  class using the :mod:`~satpy.Scene.load` method with the reader
  ``"fci_l1c_nc"``.
docstr: Load the index map for an FCI channel.
docstr_tok: ["Load","the","index","map","for","an","FCI","channel","."]
code: def _get_dataset_index_map(self, dsname):
      """Load the index map for an FCI channel."""
      grp_path = self.get_channel_measured_group_path(
          _get_channel_name_from_dsname(dsname)
      )
      dv_path = grp_path + "/index_map"
      data = self[dv_path]
  
      data = data.where(data != data.attrs.get("_FillValue", 65535))
      return data
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  from datetime import timedelta
  from functools import cached_property
  import dask.array
  import numpy
  import xarray
  from netCDF4 import default_fillvals
  from pyresample import geometry
  from satpy.readers._geos_area import get_geos_area_naming
  from satpy.readers.eum_base import get_service_mode
  from .netcdf_utils import NetCDF4FsspecFileHandler
label_desc: Use image node_id 15 for calling the FCIL1cNCFileHandler obj's underlying member method code with example usage: obj._get_dataset_index_map(dsname) and returns: data