def stream_download(self, chunk_size: Optional[int] = None, callback: Optional[Callable] = None) -> AsyncIterator[bytes]:
        """Generator for streaming request body data.
        """
        chunk_size = chunk_size or CONTENT_CHUNK_SIZE
        async def async_gen(resp):
            while True:
                chunk = await resp.content.read(chunk_size)
                if not chunk:
                    break
                callback(chunk, resp)
        return async_gen(self.internal_response)
Generator for streaming request body data.