code: public FxmlLoadResult<NODE, CONTROLLER> afterControllerLoaded(final Consumer<CONTROLLER> onControllerLoaded) {
          ensureCorrectlyLoaded();
          return new FxmlLoadResult<>(
              node,
              controller.map(val -> {
                  onControllerLoaded.accept(val);
                  return val;
              })
          );
      }
docs: Applies the given {@link Consumer} to the wrapped {@link FxmlController} if its load (and its node's) was
  successful.
  
  @param onControllerLoaded The post-processing to execute on the controller
  
  @return A new instance of {@link FxmlLoadResult} with updated internal state.