class_docstr: Test SEVIRI base.
docstr: Test the rouding of start/end_time.
docstr_tok: ["Test","the","rouding","of","start\/end_time","."]
code: def test_round_nom_time(self):
      """Test the rouding of start/end_time."""
      assert round_nom_time(
          dt=self.observation_start_time(),
          time_delta=timedelta(minutes=15),
      ) == datetime(2023, 3, 20, 15, 0)
      assert round_nom_time(
          dt=self.observation_end_time(),
          time_delta=timedelta(minutes=15),
      ) == datetime(2023, 3, 20, 15, 15)
  
imports: import unittest
  from datetime import datetime, timedelta
  import dask.array
  import numpy
  import pytest
  import xarray
  from satpy.readers.seviri_base import MEIRINK_COEFS, MEIRINK_EPOCH, NoValidOrbitParams, OrbitPolynomial, OrbitPolynomialFinder, SEVIRICalibrationHandler, chebyshev, dec10216, get_cds_time, get_padding_area, get_satpos, pad_data_horizontally, pad_data_vertically, round_nom_time
  from satpy.utils import get_legacy_chunk_size
label_desc: Use image node_id 10 for calling the SeviriBaseTest obj's underlying member method code with example usage: obj.test_round_nom_time() without return types