code: def testVocabSize(self):
      num_vel_bins = 12
      encoder = music_encoders.FlattenedTextMelodyEncoderAbsolute(
          steps_per_second=4, num_velocity_bins=num_vel_bins
      )
      expected = num_vel_bins + encoder.num_reserved_ids + 2
      self.assertEqual(expected, encoder.vocab_size)
  
imports: import tempfile
  from magenta.models.score2perf import music_encoders
  import note_seq
  from note_seq import testing_lib
  import tensorflow.compat.v1
label_desc: Use image node_id 2 for calling the FlattenedTextMelodyEncoderTest obj's underlying member method code with example usage: obj.testVocabSize() without return types