def add(self, start, end=_empty):
        """
        Add another range

        @type start: C{int}
        @param start: Start of range, or only message number

        @type end: Optional C{int}
        @param end: End of range.
        """
        if end is self._empty:
            end = start

        if self._last is not self._empty:
            if start is None:
                start = self.last
            if end is None:
                end = self.last

        if start > end:
            # Try to keep in low, high order if possible
            # (But we don't know what None means, this will keep
            # None at the start of the ranges list)
            start, end = end, start

        self.ranges.append((start, end))
        self.clean()
dataset/ETHPy150Open nlloyd/SubliminalCollaborator/libs/twisted/mail/imap4.py/MessageSet.add/original