code: function serializeObject( object, indent = INDENT, pad = 0, space ) {
     const properties = Object.keys( object )
        .map( key => serializeKey( key ) + ': ' +
                     serialize( object[ key ], indent, pad + indent, space ) );
  
     return '{' + serializeList( properties, indent, pad, space ) + '}';
  }
docs: Serialize an object.
  @private
  @param {Object} object the object to serialize
  @param {Number} [indent] the number of spaces to use for indent
  @param {Number} [pad] the initial left padding
  @param {String} [space] the character(s) to use for padding
  @return {String} the serialized JavaScript code