code: def create_token_indices(self, tokens):
          
          start_index = len(self.special_token)
          indices = list(range(len(tokens) + start_index))
          # prepend because the special tokens come in the beginning
          tokens_with_special = self.special_token + list(tokens)
          self._token2idx = dict(list(zip(tokens_with_special, indices)))
          self._idx2token = dict(list(zip(indices, tokens_with_special)))
docs: If `apply_encoding_options` is inadequate, one can retrieve tokens from `self.token_counts`, filter with
          a desired strategy and regenerate `token_index` using this method. The token index is subsequently used
          when `encode_texts` or `decode_texts` methods are called.