rowShouldUpdate(sectionIndex: number, rowIndex: number): boolean {
    var needsUpdate = this._dirtyRows[sectionIndex][rowIndex];
    warning(
      needsUpdate !== undefined,
      'missing dirtyBit for section, row: ' + sectionIndex + ', ' + rowIndex,
    );
    return needsUpdate;
  }
Returns if the row is dirtied and needs to be rerendered