declare namespace Ext {
    export namespace util {
        export interface CollectionKeyConfig {
            keyFn?: string | CallableFunction;
            property?: string;
            rootProperty?: string;
        }

        export class CollectionKey extends Ext.Base  {
            public name?: string;
            public get(key?: any): object;
            public getKeyFn(): void;
            public getProperty(): void;
            public getRootProperty(): void;
            public indexOf(key?: any, startAt?: number): number;
            public setKeyFn(): void;
            public setProperty(): void;
            public setRootProperty(): void;
            public updateKey(item?: object, oldKey?: string): void;
        }
    }
}