code: def save_stream(self, key, binary=False):
          
          mode = 'wb' if binary else 'w'
          with open(os.path.join(self.uri, key), mode) as f:
              yield f
docs: Yield a file object representing `key`
  
          :param str key: The file to save to
          :param bool binary: Whether we should treat it as binary
          :return: