async def write_and_drain(self, data: bytes, timeout: NumType = None) -> None:
        """
        Format a command and send it to the server.
        """
        if self._stream_writer is None:
            raise SMTPServerDisconnected("Client not connected")

        self._stream_writer.write(data)

        async with self._io_lock:
            await self._drain_writer(timeout)
Format a command and send it to the server.