class_docstr: Predict next line of poetry from the last line. From Gutenberg texts.
code: def approx_vocab_size(self):
      return 2**13
  
file_path: tensor2tensor/tensor2tensor/test_data/example_usr_dir/my_submodule.py
imports: import re
  from tensor2tensor.data_generators import problem
  from tensor2tensor.data_generators import text_problems
  from tensor2tensor.layers import common_hparams
  from tensor2tensor.utils import registry
label_desc: Use image node_id 1 for calling the PoetryLines obj's underlying member method code with example usage: obj.approx_vocab_size() and returns: unknown