sanic streamed response

streamed_response.py

class StreamResponse(HTTPResponse):
    def __init__(self, request, length, status=200, headers=None,
                 content_type='text/plain', ):
        self.request = request
        self.length = length
        self._headers_sent = False
        headers = headers or {}
        headers['Content-Length'] = str(length)
        super().__init__(None, status, headers, content_type)

    def send_headers(self, keep_alive=True, keep_alive_timeout=60):
        if self._headers_sent:
            raise Exception('Headers already sent')
        self.request.transport.write(
            super().output(self.request.version, keep_alive, keep_alive_timeout)
        )
        self._headers_sent = True

    def write(self, chunk):
        if not self._headers_sent:
            raise Exception('Must send headers before writing')
        self.transport.write(chunk)

    def output(self, *args):
        if not self._headers_sent:
            raise Exception('Must send headers before finishing')
        return b''