export declare const ERROR_MESSAGES: {
    INVALID_URL: (details: string) => string;
    INVALID_PROTOCOL: (protocol: string) => string;
    ROBOTS_DENIED: (url: string, userAgent: string) => string;
    ROBOTS_UNREACHABLE: (details: string) => string;
    ROBOTS_CRAWL_DELAY: (delay: number) => string;
    DEFAULT_BLOCK: string;
};