/**
 * Creates a new object by prepending a specified string to each key of the original object.
 *
 * @example
 * const original = { name: 'Alice', age: 30 };
 * prependKeys(original, 'user_') // { user_name: 'Alice', user_age: 30 }
 *
 * @param obj The original object.
 * @param prefix The string to prepend to each key.
 * @returns A new object with modified keys.
 */
export declare function prependKeys<T extends Record<string, any>, P extends string>(obj: T | null | undefined, prefix: P): {
    [K in keyof T as `${P}${string & K}`]: T[K];
};