def is_streamed(self) -> bool:
        """If the response is streamed (the response is not an iterable with
        a length information) this property is `True`.  In this case streamed
        means that there is no information about the number of iterations.
        This is usually `True` if a generator is passed to the response object.

        This is useful for checking before applying some sort of post
        filtering that should not take place for streamed responses.
        """
        try:
            len(self.response)  # type: ignore
        except (TypeError, AttributeError):
            return True
        return False
If the response is streamed (the response is not an iterable with
        a length information) this property is `True`.  In this case streamed
        means that there is no information about the number of iterations.
        This is usually `True` if a generator is passed to the response object.

        This is useful for checking before applying some sort of post
        filtering that should not take place for streamed responses.
        
src/werkzeug/wrappers/response.py