Create the stream
        
        :param stream_id: The stream identifier
        :param sandbox: The sandbox for this stream
        :return: None
        :raises: NotImplementedError

def create_stream(self, stream_id, sandbox=None):
        """
        Create the stream
        
        :param stream_id: The stream identifier
        :param sandbox: The sandbox for this stream
        :return: None
        :raises: NotImplementedError
        """
        if sandbox is not None:
            raise NotImplementedError

        logging.debug("Creating asset stream {}".format(stream_id))

        if stream_id in self.streams:
            raise StreamAlreadyExistsError("Stream with id '{}' already exists".format(stream_id))

        stream = AssetStream(channel=self, stream_id=stream_id, calculated_intervals=None,
                             last_accessed=utcnow(), last_updated=utcnow(), sandbox=sandbox)
        self.streams[stream_id] = stream
        return stream