/**
 * Creates a new object by mapping all string properties (keys and values) of an existing object
 * through a mapper function.
 *
 * @param obj - The source object, whose properties will be mapped.
 * @param fn - The mapper function.
 *
 * @returns A new object with the properties mapped to the new type.
 *
 * @internal
 * @hidden
 */
export declare function mapKeyValues<T extends Record<string, any>, U>(obj: T, fn: (key: keyof T & string, value: T[keyof T & string]) => U): Record<keyof T, U>;