declare namespace Ext {
    export namespace util {
        export interface GrouperConfig {
            direction?: string;
            groupFn?: CallableFunction;
            id?: any;
            property?: string;
            root?: string;
            sorterFn?: CallableFunction;
            sortProperty?: string;
            transform?: CallableFunction;
        }

        export class Grouper extends Ext.util.Sorter  {
            public getGroupFn(): void;
            public getGroupString(item?: Ext.data.Model): string;
            public getSortProperty(): void;
            public setGroupFn(): void;
            public setSortProperty(): void;
        }
    }
}