code: public static Set<Node> prepareSingleNodeSet(Set<BioPAXElement> elements, Graph graph)
  	{
  		Map<BioPAXElement, Set<PhysicalEntity>> map = getRelatedPhysicalEntityMap(elements);
  
  		Set<PhysicalEntity> pes = new HashSet<PhysicalEntity>();
  		for (Set<PhysicalEntity> valueSet : map.values())
  		{
  			pes.addAll(valueSet);
  		}
  
  		Set<Node> nodes = graph.getWrapperSet(pes);
  
  		// If there are interactions in the seed add them too
  
  		Set<Node> inters = getSeedInteractions(elements, graph);
  		nodes.addAll(inters);
  
  		return nodes;
  	}
docs: Gets the related wrappers of the given elements in a set.
  @param elements Elements to get the related wrappers
  @param graph Owner graph
  @return Related wrappers in a set