export interface LogFn {
    (msg: string, ...args: any[]): void;
    (obj: object, msg?: string, ...args: any[]): void;
}
export declare enum LogLevel {
    FATAL = "fatal",
    ERROR = "error",
    WARN = "warn",
    INFO = "info",
    DEBUG = "debug",
    TRACE = "trace"
}
export interface Logger {
    /**
     * Log at `'fatal'` level the given msg. If the first argument is an object, all its properties will be included in the JSON line.
     * If more args follows `msg`, these will be used to format `msg` using `util.format`.
     *
     * @param obj: object to be serialized
     * @param msg: the log message to write
     * @param ...args: format string values when `msg` is a format string
     */
    fatal: LogFn;
    /**
     * Log at `'error'` level the given msg. If the first argument is an object, all its properties will be included in the JSON line.
     * If more args follows `msg`, these will be used to format `msg` using `util.format`.
     *
     * @param obj: object to be serialized
     * @param msg: the log message to write
     * @param ...args: format string values when `msg` is a format string
     */
    error: LogFn;
    /**
     * Log at `'warn'` level the given msg. If the first argument is an object, all its properties will be included in the JSON line.
     * If more args follows `msg`, these will be used to format `msg` using `util.format`.
     *
     * @param obj: object to be serialized
     * @param msg: the log message to write
     * @param ...args: format string values when `msg` is a format string
     */
    warn: LogFn;
    /**
     * Log at `'info'` level the given msg. If the first argument is an object, all its properties will be included in the JSON line.
     * If more args follows `msg`, these will be used to format `msg` using `util.format`.
     *
     * @param obj: object to be serialized
     * @param msg: the log message to write
     * @param ...args: format string values when `msg` is a format string
     */
    info: LogFn;
    /**
     * Log at `'debug'` level the given msg. If the first argument is an object, all its properties will be included in the JSON line.
     * If more args follows `msg`, these will be used to format `msg` using `util.format`.
     *
     * @param obj: object to be serialized
     * @param msg: the log message to write
     * @param ...args: format string values when `msg` is a format string
     */
    debug: LogFn;
    /**
     * Log at `'trace'` level the given msg. If the first argument is an object, all its properties will be included in the JSON line.
     * If more args follows `msg`, these will be used to format `msg` using `util.format`.
     *
     * @param obj: object to be serialized
     * @param msg: the log message to write
     * @param ...args: format string values when `msg` is a format string
     */
    trace: LogFn;
}