    def num_special_tokens_to_add(self, pair=False):
        """
        Returns the number of added tokens when encoding a sequence with special tokens.

        Args:
            pair(bool):
                Whether the input is a sequence pair or a single sequence.
                Defaults to `False` and the input is a single sequence.

        Returns:
            int: Number of tokens added to sequences.
        """
        token_ids_0 = []
        token_ids_1 = []
        return len(
            self.build_inputs_with_special_tokens(token_ids_0, token_ids_1
            if pair else None))
Returns the number of added tokens when encoding a sequence with special tokens.

Args:
pair(bool):
Whether the input is a sequence pair or a single sequence.
Defaults to `False` and the input is a single sequence.

Returns:
int: Number of tokens added to sequences.
ptstructure/vqa/pytorchnlp/transformers/bert/tokenizer.py