class_docstr: Test the IciL1bNCFileHandler reader.
class_docstr_tok: ["Test","the","IciL1bNCFileHandler","reader","."]
docstr: Test interpolate returns none if dataset not exist.
docstr_tok: ["Test","interpolate","returns","none","if","dataset","not","exist","."]
code: def test_interpolate_returns_none_if_dataset_not_exist(self, reader):
      """Test interpolate returns none if dataset not exist."""
      azimuth, zenith = reader._interpolate(
          InterpolationType.OBSERVATION_ANGLES
      )
      assert azimuth is None
      assert zenith is None
  
imports: from datetime import datetime
  from unittest.mock import patch
  import numpy
  import pytest
  import xarray
  from netCDF4 import Dataset
  from satpy.readers.ici_l1b_nc import IciL1bNCFileHandler, InterpolationType
label_desc: Use image node_id 23 for calling the TestIciL1bNCFileHandler obj's underlying member method code with example usage: obj.test_interpolate_returns_none_if_dataset_not_exist(reader) without return types