def add_label(self, label):
        """Add label to list of labels on the message."""
        if isinstance(label, str):
            if label not in self._labels:
                self._labels.append(label)
        else:
            raise TypeError('label must be a string: %s' % type(label))
dataset/ETHPy150Open babble/babble/include/jython/Lib/mailbox.py/BabylMessage.add_label/original