code: @Nullable
      public final Controller getTargetController() {
          if (targetInstanceId != null) {
              return router.getRootRouter().getControllerWithInstanceId(targetInstanceId);
          }
          return null;
      }
docs: Returns the target Controller that was set with the {@link #setTargetController(Controller)}
  method or {@code null} if this Controller has no target.
  
  @return This Controller's target