/**
 * Groups array elements by a key function, similar to Object.groupBy
 * @param items - Array of items to group
 * @param keyFn - Function that extracts the grouping key from each item
 * @returns Object with keys as group identifiers and values as arrays of grouped items
 */
export declare function groupBy<T>(items: T[], keyFn: (item: T) => string | number | symbol): Record<string | number | symbol, T[]>;