/**
 * Sets the last name of the current user.
 *
 * @param lastName - Limited to 255 characters in length. Accepts an explicit null value to null out attribute.
 *
 * @returns Resolves to a boolean that indicates whether the update was successfully enqueued. Resolves to undefined
 *   if the SDK is not initialized.
 */
export declare function setUserLastName(lastName: string | null): Promise<boolean | undefined>;