code: public static void loadPageFlow(ServletRequest request, PageFlowController pageFlow) {
          if(pageFlow != null)
              request.setAttribute(PAGE_FLOW_IMPLICIT_OBJECT_KEY, pageFlow);
  
          Map map = InternalUtils.getPageInputMap(request);
          request.setAttribute(PAGE_INPUT_IMPLICIT_OBJECT_KEY, map != null ? map : Collections.EMPTY_MAP);
      }
docs: Load Page Flow related implicit objects into the request.  This method will set the
  Page Flow itself and any available page inputs into the request.
  @param request the request
  @param pageFlow the current page flow