class_docstr: Test how metadata is combined.
class_docstr_tok: ["Test","how","metadata","is","combined","."]
docstr: Test combining nan fill values.
docstr_tok: ["Test","combining","nan","fill","values","."]
code: def test_combine_nans(self):
      """Test combining nan fill values."""
      from satpy.dataset.metadata import combine_metadata
  
      test_metadata = [{"_FillValue": np.nan}, {"_FillValue": np.nan}]
      assert combine_metadata(*test_metadata) == {"_FillValue": np.nan}
  
imports: import unittest
  from datetime import datetime
  import numpy
  import pytest
  from satpy.dataset.dataid import DataID, DataQuery, ModifierTuple, WavelengthRange, minimal_default_keys_config
  from satpy.readers.pmw_channels_definitions import FrequencyDoubleSideBand, FrequencyQuadrupleSideBand, FrequencyRange
  from satpy.tests.utils import make_cid, make_dataid, make_dsq
label_desc: Use image node_id 11 for calling the TestCombineMetadata obj's underlying member method code with example usage: obj.test_combine_nans() without return types