def METHOD_NAME(self, special_tokens):
    """ Add a list of additional tokens to the encoder.
        The additional tokens are indexed starting from the last
        index of the
        current vocabulary in the order of the `special_tokens` list.
    """
    if not special_tokens:
        self.special_tokens = {}
        self.special_tokens_decoder = {}
        return
    new = dict(
        (tok, self.code_column.vocab_size + i)
        for i, tok in enumerate(special_tokens)
        if tok not in self.special_tokens
    )
    self.special_tokens.update(new)
    self.special_tokens_decoder = {v: k for k, v in self.special_tokens.items()}