code: def testSetLengthRemoveStepsFromSequenceWithoutEnd(self):
      poly_seq = polyphony_lib.PolyphonicSequence(steps_per_quarter=1)
  
      # Construct a list with two silence steps and no END.
      pe = polyphony_lib.PolyphonicEvent
      poly_seq.append(pe(pe.STEP_END, None))
      poly_seq.append(pe(pe.STEP_END, None))
  
      poly_seq.set_length(1)
      poly_events = [
          pe(pe.START, None),
          pe(pe.STEP_END, None),
          pe(pe.END, None),
      ]
      self.assertEqual(poly_events, list(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 14 for calling the PolyphonyLibTest obj's underlying member method code with example usage: obj.testSetLengthRemoveStepsFromSequenceWithoutEnd() without return types