code: def test_build_throw_exception_unk_token_not_in_vocab(self):
      vocab = [
          "a",
          "abc",
          "abcdefghi",
          "##de",
          "##defgxy",
          "##deh",
          "##f",
          "##ghz",
      ]
      max_bytes_per_token = 100
      suffix_indicator = "##"
      unk_token = "<unk>"
      with self.assertRaisesRegex(
          RuntimeError, "Cannot find unk_token in the vocab!"
      ):
          (
              pywrap_fast_wordpiece_tokenizer_model_builder.build_fast_wordpiece_model(
                  vocab,
                  max_bytes_per_token,
                  suffix_indicator,
                  unk_token,
                  True,
                  False,
              )
          )
  
file_path: text/tensorflow_text/core/pybinds/pywrap_fast_wordpiece_tokenizer_model_builder_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from tensorflow.python.framework import test_util
  from tensorflow.python.platform import gfile
  from tensorflow.python.platform import test
  from tensorflow_text.core.pybinds import pywrap_fast_wordpiece_tokenizer_model_builder
label_desc: Use image node_id 2 for calling the PywrapFastWordpieceBuilderTest obj's underlying member method code with example usage: obj.test_build_throw_exception_unk_token_not_in_vocab() without return types