class_docstr: A single training/test example for simple sequence classification.
  
  For examples without an answer, the start and end position are -1.
code: def __str__(self):
      return self.__repr__()
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  import json
  import math
  import os
  import random
  import mesh_tensorflow
  import mesh_tensorflow.bert.bert
  import mesh_tensorflow.bert.optimization
  import mesh_tensorflow.bert.tokenization
  import six
  from six.moves import range
  import tensorflow.compat.v1
  from tensorflow.compat.v1 import estimator
label_desc: Use image node_id 2 for calling the SquadExample obj's underlying member method code with example usage: obj.__str__() and returns: self