import { LogEntry, Transformer } from 'ansi-logger/AnsiLogger';
/**
 * Transform log entries JSON encoded string output.
 */
export declare class JSONTransformer implements Transformer<string> {
    readonly printer: {
        readonly err: (msg: string) => void;
        readonly out: (msg: string) => void;
    };
    constructor(printer?: {
        err: (msg: string) => void;
        out: (msg: string) => void;
    });
    /**
     * Format log entries to json strings.
     */
    format(entry: LogEntry): string;
    /**
     * Don't "format" complex types, just pass them along,
     * and let the formatting happen in the `format` method.
     */
    formatTypes<T>(msg: T): T;
}