returns a list of all token IDs in the given, left-closed,
        right-open interval (i.e. includes start_id, but excludes stop_id)

        >>> gen_token_range('T0', 'T1')
        ['T0']

        >>> gen_token_range('T1', 'T5')
        ['T1', 'T2', 'T3', 'T4']

def gen_token_range(self, start_id, stop_id):
        """
        returns a list of all token IDs in the given, left-closed,
        right-open interval (i.e. includes start_id, but excludes stop_id)

        >>> gen_token_range('T0', 'T1')
        ['T0']

        >>> gen_token_range('T1', 'T5')
        ['T1', 'T2', 'T3', 'T4']
        """
        index_range = range(self.tokenid2index(start_id), self.tokenid2index(stop_id))
        return ["T{}".format(index) for index in index_range]