Update cached user presence state from Matrix presence events.

        Due to the possibility of nodes using accounts on multiple homeservers a composite
        address state is synthesised from the cached individual user presence states.

def _presence_listener(self, event: Dict[str, Any]):
        """
        Update cached user presence state from Matrix presence events.

        Due to the possibility of nodes using accounts on multiple homeservers a composite
        address state is synthesised from the cached individual user presence states.
        """
        if self._stop_event.ready():
            return
        user_id = event['sender']
        if event['type'] != 'm.presence' or user_id == self._user_id:
            return

        user = self._get_user(user_id)
        user.displayname = event['content'].get('displayname') or user.displayname
        address = self._validate_userid_signature(user)
        if not address:
            # Malformed address - skip
            return

        # not a user we've whitelisted, skip
        if not self.is_address_known(address):
            return
        self.add_userid_for_address(address, user_id)

        new_state = UserPresence(event['content']['presence'])
        if new_state == self._userid_to_presence.get(user_id):
            # Cached presence state matches, no action required
            return

        self._userid_to_presence[user_id] = new_state
        self.refresh_address_presence(address)

        if self._user_presence_changed_callback:
            self._user_presence_changed_callback(user, new_state)