code: protected static <T> T getTracer(Class<T> intf, InterfaceTracer tracer, T ob)
      {
          tracer.setAppendable(System.err);
          tracer.setObj(ob);
          return (T) Proxy.newProxyInstance(
                  intf.getClassLoader(), 
                  new Class<?>[] {intf}, 
                  tracer);
      }
docs: Creates a tracer for intf. This is meant to be used by subclass.
  @param <T>
  @param intf Implemented interface
  @param ob Class instance for given interface or null
  @return