docs: def partition_node(node):
      """Split a host:port string into (host, int(port)) pair."""
      host = node
      port = 27017
      idx = node.rfind(':')
      if idx != -1:
          host, port = node[:idx], int(node[idx + 1:])
      if host.startswith('['):
          host = host[1:-1]
      return host, port