message: Correcting a small typo in the docs in Accessing the JSON Data
  Summary:
  As the title says.
  The `json_string` was misspelled in the code snippet
  Reviewers: jamiep, mariok, #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, georgep
  Subscribers: georgep
  Maniphest Tasks: T20288
diff: @@ -292,4 +292,4 @@ be loaded into a JSON object using the native JSON library, for example:
  with tf.Session() as sess:
  json_string = sess.run(benchmark_op)
  - json_object = json.loads(j_str[0])
  + json_object = json.loads(json_string[0])
  