def _send_accum_trace(self, device_uuid):
        """Send whatever accumulated tracing data we have for the device."""

        if device_uuid not in self._connections:
            self._logger.debug("Dropping trace data for device without an active connection, uuid=0x%X", device_uuid)
            return

        conn_data = self._connections[device_uuid]

        trace = conn_data['trace_accum']

        if len(trace) > 0:
            slug = self._build_device_slug(device_uuid)
            tracing_topic = self.topics.prefix + 'devices/{}/data/tracing'.format(slug)

            data = {'type': 'notification', 'operation': 'trace'}
            data['trace'] = binascii.hexlify(trace)
            data['trace_origin'] = device_uuid

            self._logger.debug('Publishing trace: (topic=%s)', tracing_topic)
            self.client.publish(tracing_topic, data)

        conn_data['trace_scheduled'] = False
        conn_data['last_trace'] = monotonic()
        conn_data['trace_accum'] = bytes()
Send whatever accumulated tracing data we have for the device.