docs: public void setVfsFolder(String vfsFolder) throws CmsIllegalArgumentException {
  
          if (CmsStringUtil.isEmptyOrWhitespaceOnly(vfsFolder)) {
              throw new CmsIllegalArgumentException(Messages.get().container(Messages.ERR_VALUE_EMPTY_0));
          }
          // test if it is a valid path
          if (!m_cms.existsResource(vfsFolder, CmsResourceFilter.ALL.addRequireFolder())) {
              throw new CmsIllegalArgumentException(
                  Messages.get().container(Messages.ERR_XMLCONTENT_VFSFOLDER_1, vfsFolder));
          }
          m_vfsFolder = vfsFolder;
      }