code: def testLibrispeechMultihead(self, params=None):
      self.testTransformerLibrispeech({"num_heads": 2})
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  from tensor2tensor.data_generators import librispeech
  from tensor2tensor.data_generators import problem_hparams
  from tensor2tensor.models import transformer
  import tensorflow.compat.v1
  from tensorflow.compat.v1 import estimator
label_desc: Use image node_id 4 for calling the TransformerTest obj's underlying member method code with example usage: obj.testLibrispeechMultihead(params) without return types