docs: def least_loaded_node(self):
          """Choose the node with fewest outstanding requests, with fallbacks.
  
          This method will prefer a node with an existing connection and no
          in-flight-requests. If no such node is found, a node will be chosen
          randomly from disconnected nodes that are not "blacked out" (i.e.,
          are not subject to a reconnect backoff). If no node metadata has been
          obtained, will return a bootstrap node (subject to exponential backoff).
  
          Returns:
              node_id or None if no suitable node was found
          """
          nodes = [broker.nodeId for broker in self.cluster.brokers()]
          random.shuffle(nodes)
  
          inflight = float('inf')
          found = None
          for node_id in nodes:
              conn = self._conns.get(node_id)
              connected = conn is not None and conn.connected()
              blacked_out = conn is not None and conn.blacked_out()
              curr_inflight = len(conn.in_flight_requests) if conn is not None else 0
              if connected and curr_inflight == 0:
                  # if we find an established connection
                  # with no in-flight requests, we can stop right away
                  return node_id
              elif not blacked_out and curr_inflight < inflight:
                  # otherwise if this is the best we have found so far, record that
                  inflight = curr_inflight
                  found = node_id
  
          if found is not None:
              return found
  
          return None