export declare function groupBy<T>(list: any[] | undefined, keyGetter: {
    (change: {
        groupNumber: any;
    }): any;
    (data: any): any;
    (header: any): any;
    (chart: any): any;
    (chart: any): any;
    (change: any): any;
    (change: any): string;
    (change: {
        groupNumber: any;
    }): any;
    (arg0: any): any;
}): T[];