Get the list of token_id given doc.

        Args:
            doc (list): document.

        Returns:
            list: int id of doc.

def doc2id(self, doc):
        """Get the list of token_id given doc.

        Args:
            doc (list): document.

        Returns:
            list: int id of doc.
        """
        doc = map(self.process_token, doc)
        return [self.token_to_id(token) for token in doc]