export declare function isString(value: any): value is string;
export declare function isNullOrEmpty(value: string | undefined): value is undefined;
export declare function isNullOrEmpty(value: string | null): value is null;
export declare function stringify(value: any, replacer?: any, space?: string | number): string | undefined;
declare global  {
    interface StringConstructor {
        isString: typeof isString;
        isNullOrEmpty: typeof isNullOrEmpty;
        stringify: typeof stringify;
    }
}