code: private void checkNodeRecursive(Node node)
  	{
  		if (isDangling(node))
  		{
  			removeNode(node);
  
  			for (Edge edge : node.getUpstream())
  			{
  				checkNodeRecursive(edge.getSourceNode());
  			}
  			for (Edge edge : node.getDownstream())
  			{
  				checkNodeRecursive(edge.getTargetNode());
  			}
  			for (Node parent : node.getUpperEquivalent())
  			{
  				checkNodeRecursive(parent);
  			}
  			for (Node child : node.getLowerEquivalent())
  			{
  				checkNodeRecursive(child);
  			}
  		}
  	}
docs: Recursively checks if a node is dangling.
  @param node Node to check