def __delitem__(self, member):
        element = self.value_type.encode(member)
        session = self.session
        if session.current_transaction is None:
            exists = session.client.zrem(self.key, element)
        else:
            session.mark_query()
            exists = session.client.zscore(self.key, element) is not None
            if exists:
                session.mark_manipulative()
                session.client.zrem(self.key, element)
        if not exists:
            raise KeyError(member)
Removes the ``member``.
dataset/ETHPy150Open dahlia/sider/sider/sortedset.py/SortedSet.__delitem__