old_contents: 
  
  class FileList(list):
      """
      List of unique items
      """
      def __init__(self, *args, **kwargs):
          super(FileList, self).__init__(*args, **kwargs)
          self.__s = set()
      
      def append(self, item):
          if item in self.__s:
              return False
          else:
              self.__s.add(item)
              list.append(self, item)
              return True
  
new_contents: 
  
  class UniqList(list):
      """
      List of unique items
      """
      def __init__(self, *args, **kwargs):
          super(UniqList, self).__init__(*args, **kwargs)
          self.__s = set()
      
      def append(self, item):
          if item in self.__s:
              return False
          else:
              self.__s.add(item)
              list.append(self, item)
              return True
  
subject: rename FileList -> UniqList