whole_func_string: function () {
          var values = this.getValue(),
              key;
          for (key in values) {
              if (values[key] !== undefined) {
                  return true;
              }
          }
          return false;
      }
func_code_string: function () {
          var values = this.getValue(),
              key;
          for (key in values) {
              if (values[key] !== undefined) {
                  return true;
              }
          }
          return false;
      }
func_documentation_string: Template method that is to return <tt>true</tt> if the filter
  has enough configuration information to be activated.
  @return {Boolean}