class_docstr: Problem spec for Librispeech using clean and noisy data.
code: def num_dev_shards(self):
      return 1
  
imports: import os
  import tarfile
  from tensor2tensor.data_generators import generator_utils
  from tensor2tensor.data_generators import problem
  from tensor2tensor.data_generators import speech_recognition
  from tensor2tensor.utils import registry
  from tensorflow.compat.v1 import estimator
label_desc: Use image node_id 3 for calling the Librispeech obj's underlying member method code with example usage: obj.num_dev_shards() and returns: int