# File lib/graphviz.rb, line 484
484:   def <<( oNode )
485:     raise( ArgumentError, "Edge between root graph and node or cluster not allowed!" ) if self.pg.nil?
486: 
487:     if( oNode.class == Array ) 
488:       oNode.each do |no|
489:         self << no
490:       end
491:     else
492:       return GraphViz::commonGraph( oNode, self ).add_edge( self, oNode )
493:     end
494:   end