code: func (g *Graph) AddNodes(g2 *Graph) *Graph {
  
  	if g == nil {
  		return nil
  	}
  
  	if g2 != nil {
  		g.Out = append(g.Out, g2.Out...)
  	}
  	return g
  }
docs: // AddNodes adds subnodes of the given Graph to the current node.