code: function format(arg) {
      if (typeof arg === 'number') {
          return '0x' + arg.toString(16).toUpperCase();
      }
  
      if (typeof arg === 'string') {
          return '"' + arg + '"';
      }
  
      return arg.toString();
  }
docs: Format an argument to be displayed in the error message
  
  @private
  @param {*} arg Argument to format
  @return {string} Formatted argument