         // recurse into the nested arrays
          if (!this._arrayEquals(arr1[i], arr2[i])) {
            return false;
          }
        } else if (arr1[i] != arr2[i]) {
          return false;
        }
      }
      return true;
    }

    /** @protected */
    _checkImports() {
      [
        'vaadin-grid-column-group',
        'vaadin-grid-filter',
        'vaadin-grid-filter-column',
        'vaadin-grid-tree-toggle',
        'vaadin-grid-selection-column',
        'vaadin-grid-sort-column',
   