code: public void visit(BioPAXElement domain, Object range, Model targetModel, PropertyEditor editor)
  	{
  		BioPAXElement targetDomain = targetModel.getByID(domain.getUri());
  		
  		if (range instanceof BioPAXElement)
  		{
  			BioPAXElement bpe = (BioPAXElement) range;
  			BioPAXElement existing = targetModel.getByID(bpe.getUri());
  			//set the property value if the value is already present in the target 
  			if (existing != null) {
  				editor.setValueToBean(existing, targetDomain);
  			}
  		}
  		else
  		{
  			editor.setValueToBean(range, targetDomain);
  		}
  	}
docs: Implement interface: Visitor