class_docstr: Test the get_dataset method.
docstr: Test getting the channel datasets when no TLEs are present.
code: def test_get_dataset_no_tle(self, get_channel, *mocks):
      """Test getting the channel datasets when no TLEs are present."""
      pygac_reader = _get_reader_mocked()
      pygac_reader.get_tle_lines = mock.MagicMock()
      pygac_reader.get_tle_lines.side_effect = RuntimeError()
  
      fh = self._create_file_handler(pygac_reader)
  
      # Test calibration to reflectance as well as attributes.
      key, res = self._get_dataset(fh)
      exp = self._create_expected(res.name)
      xr.testing.assert_identical(res, exp)
      get_channel.assert_called_with(key)
  
      self._check_get_channel_calls(fh, get_channel)
  
imports: from datetime import datetime
  from unittest import TestCase, mock
  import dask.array
  import numpy
  import pytest
  import xarray
label_desc: Use image node_id 6 for calling the TestGetDataset obj's underlying member method code with example usage: obj.test_get_dataset_no_tle(get_channel) without return types