export type ItemKeyResolver<T> = (item: T) => string | number | symbol;
interface ItemKeyHelpers<T> {
    getKey: (item: T) => unknown;
    equals: (a: T, b: T) => boolean;
    findIndex: (items: T[], item: T) => number;
    toKeySet: (items: T[]) => Set<unknown>;
    filterOut: (items: T[], removal: T[]) => T[];
}
export declare function createItemKeyHelpers<T>(itemKey?: ItemKeyResolver<T>): ItemKeyHelpers<T>;
export {};