class_docstr: Tests text data class.
      
docstr: Tests prefetching.
          
docstr_tok: ["Tests","prefetching","."]
code: def test_prefetch(self):
      """Tests prefetching."""
      hparams = copy.copy(self._hparams)
      hparams.update({"prefetch_buffer_size": 2})
      self._run_and_test(hparams)
  
imports: import tempfile
  import copy
  import numpy
  import tensorflow
  import texar.tf
label_desc: Use image node_id 7 for calling the MonoTextDataTest obj's underlying member method code with example usage: obj.test_prefetch() without return types