How to get track ID from gstdsexample.cpp in deepstream4.0.1?

Accelerated Computing Intelligent Video Analytics DeepStream SDK
#1

Hi,
My platform TX2 jetpack4.2.2 DS4.0.1.
I enabled tracker from deepstream_app_config, and could see the track ID from frame.
such as car 6;
But I want to get the track ID value for each object,I only could get object label from obj_meta->obj_label, do you have any way to get it?

thanks

[tracker]
enable=1
tracker-width=1920
tracker-height=1080
gpu-id=0
#ll-lib-file=/opt/nvidia/deepstream/deepstream-4.0/lib/libnvds_mot_klt.so
ll-lib-file=/opt/nvidia/deepstream/deepstream-4.0/lib/libnvds_nvdcf.so
ll-config-file=tracker_config.yml
enable-batch-process=1
#2

refer https://docs.nvidia.com/metropolis/deepstream/4.0/dev-guide/DeepStream_Development_Guide/baggage/struct__NvDsObjectMeta.html#a05c043991bdf68a50e1844ae92283337

/** Unique ID for tracking the object. @ref UNTRACKED_OBJECT_ID indicates the

  • object has not been tracked */
    guint64 object_id;
#3