Removes a connection_id from the registry.

        Args:
            connection_id (str): A unique identifier which identifies an
                connection on the network server socket.

def unregister_peer(self, connection_id):
        """Removes a connection_id from the registry.

        Args:
            connection_id (str): A unique identifier which identifies an
                connection on the network server socket.
        """
        public_key = self.peer_to_public_key(connection_id)
        if public_key:
            self._consensus_notifier.notify_peer_disconnected(public_key)

        with self._lock:
            if connection_id in self._peers:
                del self._peers[connection_id]
                LOGGER.debug("Removed connection_id %s, "
                             "connected identities are now %s",
                             connection_id, self._peers)
                self._topology.set_connection_status(connection_id,
                                                     PeerStatus.TEMP)
            else:
                LOGGER.warning("Connection unregister failed as connection "
                               "was not registered: %s",
                               connection_id)