code: function mode() {
        var value = (attr.mdMode || "").trim();
        if (value) {
          switch (value) {
            case MODE_DETERMINATE:
            case MODE_INDETERMINATE:
            case MODE_BUFFER:
            case MODE_QUERY:
              break;
            default:
              value = MODE_INDETERMINATE;
              break;
          }
        }
        return value;
      }
docs: Is the md-mode a valid option?