code: def test_model_loading(self):
      for (
          pretrained_model_name
      ) in XLNetTokenizer.available_checkpoints():
          tokenizer = XLNetTokenizer(
              pretrained_model_name=pretrained_model_name
          )
          _ = tokenizer.map_text_to_token("This is a test")
  
imports: import os
  import pickle
  import tempfile
  import tensorflow
  from texar.tf.data.data_utils import maybe_download
  from texar.tf.data.tokenizers.xlnet_tokenizer import XLNetTokenizer, SPIECE_UNDERLINE
  from texar.tf.utils.test import pretrained_test
label_desc: Use image node_id 3 for calling the XLNetTokenizerTest obj's underlying member method code with example usage: obj.test_model_loading() without return types