import { DVCLogger } from '@devcycle/types';
export declare const isValidDate: (date: Date | null) => date is Date;
export declare function getEnvironmentConfig({ logger, url, requestTimeout, currentEtag, currentLastModified, sseLastModified, }: {
    logger: DVCLogger;
    url: string;
    requestTimeout: number;
    currentEtag?: string;
    currentLastModified?: string;
    sseLastModified?: string;
}): Promise<Response>;