def convert_tokens_to_string(self, tokens):
        """ Converts a sequence of tokens (string) in a single string. """
        text = "".join(tokens)
        text = bytearray([self.byte_decoder[c] for c in text]).decode("utf-8", errors=self.errors)
        return text
 Converts a sequence of tokens (string) in a single string. 
xtune/src/transformers/tokenization_gpt2.py