code: def testFromQuantizedNoteSequence(self):
      testing_lib.add_track_to_sequence(
          self.note_sequence,
          0,
          [
              (60, 100, 0.0, 4.0),
              (64, 100, 0.0, 3.0),
              (67, 100, 1.0, 2.0),
          ],
      )
      quantized_sequence = sequences_lib.quantize_note_sequence(
          self.note_sequence, steps_per_quarter=1
      )
      poly_seq = list(
          polyphony_lib.PolyphonicSequence(quantized_sequence)
      )
  
      pe = polyphony_lib.PolyphonicEvent
      expected_poly_seq = [
          pe(pe.START, None),
          # step 0
          pe(pe.NEW_NOTE, 64),
          pe(pe.NEW_NOTE, 60),
          pe(pe.STEP_END, None),
          # step 1
          pe(pe.NEW_NOTE, 67),
          pe(pe.CONTINUED_NOTE, 64),
          pe(pe.CONTINUED_NOTE, 60),
          pe(pe.STEP_END, None),
          # step 2
          pe(pe.CONTINUED_NOTE, 64),
          pe(pe.CONTINUED_NOTE, 60),
          pe(pe.STEP_END, None),
          # step 3
          pe(pe.CONTINUED_NOTE, 60),
          pe(pe.STEP_END, None),
          pe(pe.END, None),
      ]
      self.assertEqual(expected_poly_seq, poly_seq)
  
imports: import copy
  from magenta.common import testing_lib
  from magenta.models.polyphony_rnn import polyphony_lib
  from note_seq import sequences_lib
  from note_seq import testing_lib
  from note_seq.protobuf import music_pb2
  import tensorflow.compat.v1
label_desc: Use image node_id 2 for calling the PolyphonyLibTest obj's underlying member method code with example usage: obj.testFromQuantizedNoteSequence() without return types