code: function format( type, args ) {
    var now = new Date().toISOString(),
      tmpl = '[%s] %s: %s\n',
      msg;
  
    msg = args[ 0 ] instanceof Error ? args[ 0 ].stack :
      util.format.apply( util, args );
  
    return util.format( tmpl, now, type, msg );
  }
docs: format log messages