code: function renameFile (oldFile, newFile) {
      if (!isFileRegistered(oldFile) || isFileRegistered(newFile)) { return undefined; }
  
      let item = fileRegistry[oldFile];
  
      item.file = newFile;
  
      fileRegistry[newFile] = item;
  
      delete fileRegistry[oldFile];
  }
docs: Unregister old file and register new one.
  
  @function renameFile
  @param {String} oldFile
  @param {String} newFile
  @api private