# File lib/graphviz.rb, line 352
352:   def <<( oNode )
353:     raise( ArgumentError, "Edge between root graph and node or cluster not allowed!" ) if self.pg.nil?
354: 
355:     if( oNode.class == Array ) 
356:       oNode.each do |no|
357:         self << no
358:       end
359:     else
360:       return GraphViz::commonGraph( oNode, self ).add_edge( self, oNode )
361:     end
362:   end