code: @Override
      public boolean isKeepMessages()
      {
          FacesContext facesContext = FacesContext.getCurrentInstance();
          ExternalContext externalContext = facesContext.getExternalContext();
          Map<String, Object> requestMap = externalContext.getRequestMap();
          Boolean keepMessages = (Boolean) requestMap.get(FLASH_KEEP_MESSAGES);
          
          return (keepMessages == null ? Boolean.FALSE : keepMessages);
      }
docs: Returns the value of a previous call to setKeepMessages() from this
  request. If there was no call yet, false is returned.