code: def render_transparent_chit():
      
  
      if request.if_none_match.contains('chit') or request.if_modified_since:
          return 'Not modified', 304
  
      out_bytes = base64.b64decode(
          "R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7")
      return out_bytes, {'Content-Type': 'image/gif', 'ETag': 'chit',
                         'Last-Modified': 'Tue, 31 Jul 1990 08:00:00 -0000'}
docs: Render a transparent chit for external, sized images