          """
          if self._previewcache.get("images", None) is None:
              logger.debug("No images in cache. Returning None")
              return None
          samples = self._previewcache["images"].copy()
          num_images, thumbnail_size = samples.shape[:2]
          if self._previewcache["placeholder"] is None:
              self._create_placeholder(thumbnail_size)
  
          logger.debug("num_images: %s, thumbnail_size: %s", num_images, thumbnail_size)
 
</s> remove         samples = []
 </s> add         samples: List[np.ndarray] = [] </s> remove                       if os.path.getmtime(fname) > self._previewcache["modified"]]
 </s> add                       if os.path.getmtime(fname) > cast(float, self._previewcache["modified"])] </s> remove         if dropped_files:
            logger.debug("Removing dropped files: %s", dropped_files)
            show_files = [fname for fname in show_files if fname not in dropped_files]

        self._previewcache["filenames"] = (self._previewcache["filenames"] +
                                           show_files)[-num_images:]
        cache = self._previewcache["images"]
 </s> add         self._previewcache["filenames"] = (cast(List[str], self._previewcache["filenames"]) +
                                           filenames)[-num_images:]
        cache = cast(Optional[np.ndarray], self._previewcache["images"]) </s> remove         retval = dict()
 </s> add         retval = {}
        samples = cast(np.ndarray, self._previewcache["images"]).copy()
          """
          if self._previewcache.get("images", None) is None:
              logger.debug("No images in cache. Returning None")
              return None
        samples = cast(np.ndarray, self._previewcache["images"]).copy()
          num_images, thumbnail_size = samples.shape[:2]
          if self._previewcache["placeholder"] is None:
              self._create_placeholder(thumbnail_size)
  
          logger.debug("num_images: %s, thumbnail_size: %s", num_images, thumbnail_size)
keep keep keep keep replace keep keep keep keep keep
 Bugfix: Preview for extract in batch mode 
lib/gui/utils.py