class_docstr: Penn Treebank data set from http://arxiv.org/pdf/1409.2329v5.pdf
  
  Arguments:
      timesteps (int): number of timesteps to embed the data
      onehot_input (bool):
      tokenizer (str): name of the tokenizer function within this
                       class to use on the data
class_docstr_tok: ["Penn","Treebank","data","set","from","http",":","\/\/arxiv.org\/pdf\/1409.2329v5.pdf","Arguments",":","timesteps","(","int",")",":","number","of","timesteps","to","embed","the","data","onehot_input","(","bool",")",":","tokenizer","(","str",")",":","name","of","the","tokenizer","function","within","this","class","to","use","on","the","data"]
docstr: Filename generator.
  
  Arguments:
      phase(str): Phase
  
  Returns:
      string: ptb.<phase>.txt
docstr_tok: ["Filename","generator",".","Arguments",":","phase","(","str",")",":","Phase","Returns",":","string",":","ptb.","<","phase",">",".txt"]
code: def gen_filename(phase):
      """
      Filename generator.
  
      Arguments:
          phase(str): Phase
  
      Returns:
          string: ptb.<phase>.txt
  
      """
      return "ptb.%s.txt" % phase
  
imports: import logging
  import numpy
  import os
  import h5py
  from neon.data.dataiterator import NervanaDataIterator, ArrayIterator
  from neon.data.datasets import Dataset
  from neon.data.text_preprocessing import pad_sentences, pad_data
label_desc: Use image node_id 3 for calling the PTB obj's underlying member method code with example usage: obj.gen_filename(phase) and returns: unknown