code: def debug(*args, **kwargs):
      
      if kwargs.get('file', None) is None:
          kwargs['file'] = sys.stderr
      msg = kwargs.get('sep', ' ').join(str(a) for a in args)
      print('debug: {}'.format(msg), **kwargs)
docs: Just prints to stderr, unless printdebug is installed. Then it
          will be replaced in `main()` by `printdebug.debug`.