class_docstr: Test the MWSL1BFile reader.
docstr: Test acquiring the start time.
docstr_tok: ["Test","acquiring","the","start","time","."]
code: def test_start_time(self, reader):
      """Test acquiring the start time."""
      assert reader.start_time == datetime(2000, 1, 2, 3, 4, 5)
  
imports: import logging
  from datetime import datetime
  from unittest.mock import patch
  import numpy
  import pytest
  import xarray
  from netCDF4 import Dataset
  from satpy.readers.mws_l1b import MWSL1BFile, get_channel_index_from_name
label_desc: Use image node_id 1 for calling the TestMwsL1bNCFileHandler obj's underlying member method code with example usage: obj.test_start_time(reader) without return types