code: private static void processXrefs(String arg) throws
  		FileNotFoundException,
  		IllegalAccessException,
  		InvocationTargetException
  	{
  		//Read in the model
          FileInputStream in =
  			new FileInputStream(new File(arg));
  		Model level2 =
  			reader.convertFromOWL(in);
  
          //Get all unification xrefs.
          Set<unificationXref> unis =
  			level2.getObjects(unificationXref.class);
  		//Create another set for avoiding concurrent modifications
          Set<unificationXref> gos = new HashSet<unificationXref>();
  
          //Process all uni. refs
          for (unificationXref uni : unis)
  		{
  			log.trace(uni.getDB());
  			//Assuming DB is represented as "GO"
              if (uni.getDB().equalsIgnoreCase("GO"))
  			{
  				//this it to avoid concurrent modification.
  				log.info("scheduling " + uni.getUri());
  				gos.add(uni);
  
  			}
  		}
          //Now we have a list of xrefs to be converted. Let's do it.
          for (unificationXref go : gos)
  		{
  			convert(go, level2);
  		}
  		//And finally write out the file. We are done !
          reader.convertToOWL(level2, new FileOutputStream(
  			arg.substring(0, arg.lastIndexOf('.')) +
  				"-converted.owl"));
  	}
docs: Main conversion method. Demonstrates how to read and write a BioPAX
  model and accessing its objects.
  @param arg file name to be processed