@defer.inlineCallbacks
    def drop(self, observed_user, observer_user):
        if not self.hs.is_mine(observer_user):
            raise SynapseError(400, "User is not hosted on this Home Server")

        yield self.store.del_presence_list(
            observer_user.localpart, observed_user.to_string()
        )

        # TODO: Inform the remote that we've dropped the presence list.
Remove a local or remote user from a local user's presence list and
dataset/ETHPy150Open matrix-org/synapse/synapse/handlers/presence.py/PresenceHandler.drop