declare function isValidProxyUrl(key: string | undefined): boolean;
declare function isHttpOrHttps(key: string | undefined): boolean;
declare function isProxyUrlRelative(key: string): boolean;
declare function proxyUrlToAbsoluteURL(url: string | undefined): string;

export { isHttpOrHttps, isProxyUrlRelative, isValidProxyUrl, proxyUrlToAbsoluteURL };