docs: public static final boolean isRequestTypeAvailable(RequestType type)
      {
          switch (type)
          {
          case SERVLET:
              return true;
  
          case ACTION:
          case RENDER:
              return _PORTLET_CONTEXT_CLASS != null;
  
          case RESOURCE:
          case EVENT:
              return _PORTLET_RENDER_REQUEST_CLASS != null;
  
          default:
              return false;
          }
      }