message: BUG: don't check tensor
diff: @@ -1123,8 +1123,10 @@ def index_to_string_table_from_file(vocabulary_file,
  ValueError: when `vocabulary_file` is empty.
  ValueError: when `vocab_size` is invalid.
  """
  - if not vocabulary_file:
  - raise ValueError("vocabulary_file must be specified.")
  + if vocabulary_file is None or (
  + isinstance(vocabulary_file, str) and not vocabulary_file):
  + raise ValueError("vocabulary_file must be specified and must not be empty.")
  +
  if vocab_size is not None and vocab_size < 1:
  raise ValueError("vocab_size must be greater than 0, got %d." % vocab_size)
  