code: public static Set<Node> getSeedInteractions(Collection<BioPAXElement> elements, Graph graph)
  	{
  		Set<Node> nodes = new HashSet<Node>();
  
  		for (BioPAXElement ele : elements)
  		{
  			if (ele instanceof Conversion || ele instanceof TemplateReaction ||
  				ele instanceof Control)
  			{
  				GraphObject go = graph.getGraphObject(ele);
  
  				if (go instanceof Node)
  				{
  					nodes.add((Node) go);
  				}
  			}
  		}
  		return nodes;
  	}
docs: Extracts the querible interactions from the elements.
  
  @param elements BioPAX elements to search
  @param graph graph model
  @return Querible Interactions (nodes)