code: def test_cf_roundtrip(fake_dnb_file, tmp_path):  # noqa
      """Test the cf writing reading cycle."""
      dnb_filename = os.fspath(fake_dnb_file)
      write_scn = Scene(
          filenames=[dnb_filename], reader="viirs_compact"
      )
      write_scn.load(["DNB"])
  
      satpy_cf_file = os.fspath(
          tmp_path / "npp-viirs-20191025061125-20191025061247.nc"
      )
      write_scn.save_datasets(writer="cf", filename=satpy_cf_file)
      read_scn = Scene(filenames=[satpy_cf_file], reader="satpy_cf_nc")
      read_scn.load(["DNB"])
  
      write_array = write_scn["DNB"]
      read_array = read_scn["DNB"]
  
      np.testing.assert_allclose(write_array.values, read_array.values)
  
imports: import os
  import numpy
  from satpy import Scene
  from satpy.tests.reader_tests.test_viirs_compact import fake_dnb, fake_dnb_file
label_desc: Use image node_id 1 for calling a global function with example usage: test_cf_roundtrip(fake_dnb_file, tmp_path) without return types