message: Change os.exists to gfile.exists.
diff: import collections
  import json
  import operator
  -import os
  import numpy as np
  @@ -35,6 +34,7 @@ from tensorflow.python.keras.utils import layer_utils
  from tensorflow.python.ops import init_ops
  from tensorflow.python.ops import lookup_ops
  from tensorflow.python.ops import math_ops
  +from tensorflow.python.platform import gfile
  from tensorflow.python.platform import tf_logging as logging
  from tensorflow.python.util import compat
  @@ -266,7 +266,7 @@ class IndexLookup(base_preprocessing_layer.CombinerPreprocessingLayer):
  # the actual data.
  initializer = _NullInitializer(self._key_dtype, self._value_dtype)
  else:
  - if not os.path.exists(vocabulary):
  + if not gfile.Exists(vocabulary):
  raise ValueError("Vocabulary file %s does not exist." % (vocabulary,))
  self._static_vocabulary_path = vocabulary
  num_tokens = table_utils.num_tokens_in_file(vocabulary)
  