export declare function notEmpty<T>(value: T | null | undefined): value is T;
export declare function ucfirst(s: string): string;
export declare function playgroundFetch(url: any, options?: any): any;
type OpenWindowOptions = {
    url: string;
    width?: number;
    height?: number;
    title?: string;
};
export declare function openWindow({ url, title, width, height, }: OpenWindowOptions): Window | null;
export {};