'Create a timestamp using a start and end time.
Args:
start: Start timestamp.
end: End timestamp.
Returns:
A tuple (start, end) of converted timestamps or None for all time.'

def _MakeTimestamp(self, start=None, end=None):

    mysql_unsigned_bigint_max = 18446744073709551615L
    ts_start = int((start or 0))
    if (end is None):
        ts_end = mysql_unsigned_bigint_max
    else:
        ts_end = int(end)
    if ((ts_start == 0) and (ts_end == mysql_unsigned_bigint_max)):
        return None
    else:
        return (ts_start, ts_end)
