Not all builtin source format are displayed in help message for import command

[sstrehlk]

Steps:
Run command
datum import --help

Expected behavior:
all built in source formats should be mentioned in help message including coco_captions, coco_image_info, coco_instances,
coco_labels, coco_panoptic, coco_person_keypoints, coco_stuff, crop_covered_segments

Current behaviour:
not all formats mentioned: