docstr: Length of each example (in tokens).
code: def sequence_length(self):
      """Length of each example (in tokens)."""
      return 32768
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import zipfile
  from tensor2tensor.data_generators import generator_utils
  from tensor2tensor.data_generators import problem
  from tensor2tensor.data_generators import text_problems
  from tensor2tensor.utils import registry
  import tensorflow.compat.v1
label_desc: Use image node_id 1 for calling the Enwik8L32k obj's underlying member method code with example usage: obj.sequence_length() and returns: int