docs: def main(args=sys.argv[1:]):
      """ main funcion of visio2img """
      if not is_pywin32_available():
          sys.stderr.write('win32com module not found')
          return -1
  
      try:
          options, argv = parse_options(args)
          export_img(argv[0], argv[1], options.pagenum, options.pagename)
          return 0
      except (IOError, OSError, IndexError) as err:
          sys.stderr.write("error: %s" % err)
          return -1