def add_sequence(self, sequence):
        """Add sequence to list of sequences including the message."""
        if isinstance(sequence, str):
            if not sequence in self._sequences:
                self._sequences.append(sequence)
        else:
            raise TypeError('sequence must be a string: %s' % type(sequence))
dataset/ETHPy150Open babble/babble/include/jython/Lib/mailbox.py/MHMessage.add_sequence/original