what is the CLASSMAP file's format?

By following the “Getting Started Guide”,

The command to use the inference on a classification model is:

  tlt-infer classification [-h] [-m MODEL] [-i IMAGE] [-d IMAGE_DIR]  [-b BATCH_SIZE] [-k KEY] [-cm CLASSMAP][-v]

  -cm CLASSMAP, --class_map CLASSMAP: The json file that specifies the class index and label mapping.

What format should this CLASSMAP json file be?

classmap is generated during training. Please check the ‘-r results_dir’ from the tlt-train command and you’ll find the classmap.json file there.