Manually chose to accept the websocket connection.

        Arguments:
            headers: Additional headers to send with the acceptance
                response.
            subprotocol: The chosen subprotocol, optional.

async def accept(
            self,
            headers: Optional[Union[dict, CIMultiDict, Headers]] = None,
            subprotocol: Optional[str] = None,
    ) -> None:
        """Manually chose to accept the websocket connection.

        Arguments:
            headers: Additional headers to send with the acceptance
                response.
            subprotocol: The chosen subprotocol, optional.
        """
        if headers is None:
            headers_ = Headers()
        else:
            headers_ = Headers(headers)
        await self._accept(headers_, subprotocol)