async def METHOD_NAME(self, user_id: int, deleter: int, reason: 'Optional[str]') -> int:
    """Delete all warnings for a user id."""
    assert isinstance(user_id, int)
    res = await self._update('warns',
                             {'deletion_time': datetime.now(), 'deletion_reason': reason, 'deleter': deleter},
                             user_id=user_id)
    if res:
        self.log.debug('Removed all warnings for %d', user_id)
    return res