def calculate_content_length(self):
        """Returns the content length if available or `None` otherwise."""
        try:
            self._ensure_sequence()
        except __HOLE__:
            return None
        return sum(len(x) for x in self.response)
dataset/ETHPy150Open Eforcers/gae-flask-todo/lib/werkzeug/wrappers.py/BaseResponse.calculate_content_length