code: function log(level, message) {
    if(!~map[this._level].indexOf(level)) return false;
    var pid = process.pid
      , time = logtime()
      , args = slice.call(arguments, 1)
      , cb = typeof args[args.length - 1] === 'function'
        ? args.pop() : null
      , stream = level === LEVELS.WARNING ? this._err : this._out;
    var msg = '[' + pid + '] ' + time + ' '
      + getPrefix(level, stream.isTTY) + ' ';
  
    if(args.length > 1) {
      message = util.format.apply(util, args);
    }else{
      message = args[0];
    }
    msg += message + EOL;
    stream.write(msg, cb);
    return message;
  }
docs: @private
  
  Log a message.
  
  If the last argument is a function it is added as a callback to
  the stream write.
  
  @param level The log level.
  @param message The log message.
  @param ... Message replacement parameters.