docs: def _check_cellpy_file(self, filename):
          """Get the file-ids for the cellpy_file."""
  
          strip_filenames = True
          check_on = self.filestatuschecker
          self.logger.debug("checking cellpy-file")
          self.logger.debug(filename)
          if not os.path.isfile(filename):
              self.logger.debug("cellpy-file does not exist")
              return None
          try:
              store = pd.HDFStore(filename)
          except Exception as e:
              self.logger.debug(f"could not open cellpy-file ({e})")
              return None
          try:
              fidtable = store.select("CellpyData/fidtable")
          except KeyError:
              self.logger.warning("no fidtable -"
                                  " you should update your hdf5-file")
              fidtable = None
          finally:
              store.close()
          if fidtable is not None:
              raw_data_files, raw_data_files_length = \
                  self._convert2fid_list(fidtable)
              txt = "contains %i res-files" % (len(raw_data_files))
              self.logger.debug(txt)
              ids = dict()
              for fid in raw_data_files:
                  full_name = fid.full_name
                  size = fid.size
                  mod = fid.last_modified
                  self.logger.debug(f"fileID information for: {full_name}")
                  self.logger.debug(f"   modified: {mod}")
                  self.logger.debug(f"   size: {size}")
  
                  if strip_filenames:
                      name = os.path.basename(full_name)
                  else:
                      name = full_name
                  if check_on == "size":
                      ids[name] = int(fid.size)
                  elif check_on == "modified":
                      ids[name] = int(fid.last_modified)
                  else:
                      ids[name] = int(fid.last_accessed)
              return ids
          else:
              return None