code: def testStretchPipeline(self):
      note_sequence = common_testing_lib.parse_test_proto(
          music_pb2.NoteSequence,
          """
          time_signatures: {
            time: 1.0
            numerator: 4
            denominator: 4}
          tempos: {
            qpm: 60}""",
      )
      testing_lib.add_track_to_sequence(
          note_sequence,
          0,
          [
              (11, 55, 0.22, 0.50),
              (40, 45, 2.50, 3.50),
              (55, 120, 4.0, 4.01),
          ],
      )
  
      expected_sequences = [
          sequences_lib.stretch_note_sequence(note_sequence, 0.5),
          sequences_lib.stretch_note_sequence(note_sequence, 1.0),
          sequences_lib.stretch_note_sequence(note_sequence, 1.5),
      ]
  
      unit = note_sequence_pipelines.StretchPipeline(
          stretch_factors=[0.5, 1.0, 1.5]
      )
      self._unit_transform_test(unit, note_sequence, expected_sequences)
  
file_path: magenta/magenta/pipelines/note_sequence_pipelines_test.py
imports: from absl.testing import absltest
  from magenta.common import testing_lib
  from magenta.pipelines import note_sequence_pipelines
  from note_seq import sequences_lib
  from note_seq import testing_lib
  from note_seq.protobuf import music_pb2
label_desc: Use image node_id 6 for calling the PipelineUnitsCommonTest obj's underlying member method code with example usage: obj.testStretchPipeline() without return types