class_docstr: NWCSAF PPS&MSG NetCDF reader.
code: def _get_filekeys(self, dsid_name, info):
      try:
          file_key = self._get_varname_in_file(
              info, info_type="file_key"
          )
      except KeyError:
          file_key = dsid_name
      return file_key
  
imports: import functools
  import logging
  import os
  from contextlib import suppress
  from datetime import datetime
  import dask.array
  import numpy
  import xarray
  from pyproj import CRS
  from pyresample.geometry import AreaDefinition
  from satpy.readers.file_handlers import BaseFileHandler
  from satpy.readers.utils import unzip_file
  from satpy.utils import get_chunk_size_limit
label_desc: Use image node_id 8 for calling the NcNWCSAF obj's underlying member method code with example usage: obj._get_filekeys(dsid_name, info) and returns: file_key