/**
 * Read properties stored in external sources like Environment Variables,
 * the credentials file, VCAP services, etc. and return them as an
 * object. The keys of this object will have the service name prefix removed
 * and will be converted to lower camel case.
 *
 * Only one source will be used at a time.
 *
 * @param serviceName - the service name prefix
 */
export declare function readExternalSources(serviceName: string): any;