export declare function group<T, K extends string | number | symbol>(arr: T[], fn: (item: T) => K): Record<K, T[]>;
export declare function groupIndices<T, K extends string | number | symbol>(arr: T[], fn: (item: T) => K): Record<K, number[]>;
export declare function findIndices<T>(arr: T[], fn: (item: T, index: number) => boolean): number[];