code: func (c *Cluster) AddNode(node *seesaw.Node) error {
  	key := node.Key()
  	if _, ok := c.Nodes[key]; ok {
  		return fmt.Errorf("Cluster %q already contains Node %q", c.Site, key)
  	}
  	c.Nodes[key] = node
  	return nil
  }
docs: // AddNode adds a Seesaw Node to a Seesaw Cluster.