class_docstr: Swap-in HDF5 File Handler.
class_docstr_tok: ["Swap-in","HDF5","File","Handler","."]
code: def _add_geo_ref(file_content, filename):
      geo_prefix = "GATMO"
      file_content["/attr/N_GEO_Ref"] = geo_prefix + filename[5:]
  
imports: import os
  from datetime import datetime
  from unittest import mock
  import numpy
  import pytest
  from satpy._config import config_search_paths
  from satpy.readers import load_reader
  from satpy.readers.atms_sdr_hdf5 import ATMS_CHANNEL_NAMES
  from satpy.readers.viirs_atms_sdr_base import DATASET_KEYS
  from satpy.tests.reader_tests.test_hdf5_utils import FakeHDF5FileHandler
label_desc: Use image node_id 8 for calling the FakeHDF5_ATMS_SDR_FileHandler obj's underlying member method code with example usage: obj._add_geo_ref(file_content, filename) without return types