code: private static Collection<Set<Node>> prepareNodeSetsFromSets(Set<Set<BioPAXElement>> sets, Graph graph)
  	{
  		Collection<Set<Node>> result = new HashSet<Set<Node>>();
  
  		for (Set<BioPAXElement> set : sets)
  		{
  			Set<Node> nodes = prepareSingleNodeSet(set, graph);
  			if (!nodes.isEmpty()) result.add(nodes);
  		}
  
  		return result;
  	}
docs: Gets the related wrappers of the given elements in individual sets. An object can be related
  to more than one wrapper and they will appear in the same set. This method created a set for
  each parameter element that has a related wrapper.
  @param sets Sets of elements to get the related wrappers
  @param graph Owner graph
  @return Related wrappers in individual sets