docs: def initialize(album_cache, image_cache, albums, images):
      """Instantiate Album or Image instances not already in cache.
  
      :param dict album_cache: Cache of Imgur albums to update. Keys are Imgur IDs, values are Album instances.
      :param dict image_cache: Cache of Imgur images to update. Keys are Imgur IDs, values are Image instances.
      :param iter albums: List of album Imgur IDs.
      :param iter images: List of image Imgur IDs.
  
      :return: Same album and image cache dictionaries from parameters.
      :rtype: tuple
      """
      if not hasattr(album_cache, 'setdefault'):
          album_cache = dict()
      if not hasattr(image_cache, 'setdefault'):
          image_cache = dict()
      for imgur_id in albums:
          album_cache.setdefault(imgur_id, Album(imgur_id))
      for imgur_id in images:
          image_cache.setdefault(imgur_id, Image(imgur_id))
      return album_cache, image_cache