/** Transforms the log object.
 * @returns transformed log, which is piped through remaining middlewares, then serialized and written to the target.
 */
export type Middleware = (data: object) => any;
/** Standard middlewares */
export declare const Middleware: {
    timestamp: <T extends object>(data: T) => T & {
        timestamp: string;
    };
    /** make 'message' and 'stack' enumerable on errors, add error type. recursive */
    error: <T extends object>(data: T) => T;
};