code: def close(self, node_id=None):
          
          with self._lock:
              if node_id is None:
                  self._close()
                  conns = list(self._conns.values())
                  self._conns.clear()
                  for conn in conns:
                      conn.close()
              elif node_id in self._conns:
                  self._conns.pop(node_id).close()
              else:
                  log.warning("Node %s not found in current connection list; skipping", node_id)
                  return
docs: Close one or all broker connections.
  
          Arguments:
              node_id (int, optional): the id of the node to close