def _get_thumbnail_filename(self, source, geometry_string, options):
key = tokey(source.key, geometry_string, serialize(options))<EOL>path = '<STR_LIT>' % (key[:<NUM_LIT:2>], key[<NUM_LIT:2>:<NUM_LIT:4>], key)<EOL>return '<STR_LIT>' % (settings.THUMBNAIL_PREFIX, path, EXTENSIONS[options['<STR_LIT>']])<EOL>
Computes the destination filename.