code: def thumbnails_for_file(relative_source_path, root=None, basedir=None,
                          subdir=None, prefix=None):
      
      if root is None:
          root = settings.MEDIA_ROOT
      if prefix is None:
          prefix = settings.THUMBNAIL_PREFIX
      if subdir is None:
          subdir = settings.THUMBNAIL_SUBDIR
      if basedir is None:
          basedir = settings.THUMBNAIL_BASEDIR
      source_dir, filename = os.path.split(relative_source_path)
      thumbs_path = os.path.join(root, basedir, source_dir, subdir)
      if not os.path.isdir(thumbs_path):
          return []
      files = all_thumbnails(thumbs_path, recursive=False, prefix=prefix,
                             subdir='')
      return files.get(filename, [])
docs: Return a list of dictionaries, one for each thumbnail belonging to the
      source image.
  
      The following list explains each key of the dictionary:
  
        `filename`  -- absolute thumbnail path
        `x` and `y` -- the size of the thumbnail
        `options`   -- list of options for this thumbnail
        `quality`   -- quality setting for this thumbnail