getSectionHeaderData(sectionIndex: number): any {
    if (!this._getSectionHeaderData) {
      return null;
    }
    var sectionID = this.sectionIdentities[sectionIndex];
    warning(
      sectionID !== undefined,
      'renderSection called on invalid section: ' + sectionIndex,
    );
    return this._getSectionHeaderData(this._dataBlob, sectionID);
  }
Gets the data required to render the section header