import tensorflow as tf

      items: the list of items to decode. These must be a subset of the item
        keys in self._items_to_handlers. If `items` is left as None, then all
        of the items in self._items_to_handlers are decoded.
    Returns:
      the decoded items, a list of tensor.
    """
    context, sequence = tf.parse_single_sequence_example(
        serialized_example, self._context_keys_to_features,
        self._sequence_keys_to_features)
    tokens_raw = sequence[self.tokens_feature_name]
    
    tokens = tf.string_split(tokens_raw, delimiter=self.delimiter).values
