def get_gae_labels(self):
        """Return the labels for GAE app.

        If the trace ID can be detected, it will be included as a label.
        Currently, no other labels are included.

        :rtype: dict
        :returns: Labels for GAE app.
        """
        gae_labels = {}

        trace_id = get_trace_id()
        if trace_id is not None:
            gae_labels[_TRACE_ID_LABEL] = trace_id

        return gae_labels