code: def dummy_image(filetype='gif'):
      
      # 1x1px Transparent GIF
      GIF = 'R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7'
      tmp_file = tempfile.NamedTemporaryFile(suffix='.%s' % filetype)
      tmp_file.write(base64.b64decode(GIF))
      return open(tmp_file.name, 'rb')
docs: Generate empty image in temporary file for testing