code: def _config_stream(filename):
      
      if filename is None or filename == '-':
          log.info('Reading config from stdin')
          yield sys.stdin
      else:
          with open(filename, mode='rt') as handle:
              log.info('Reading config from %r', filename)
              yield handle
docs: Given a configuration's filename, this returns a stream from which a configuration can be read.
  
      If `filename` is `None` or '-' then stream will be `sys.stdin`. Otherwise,
      it's the open file handle for the filename.