add custom dataset example

[zengzhaoyang]

Simple Tutorial

Training your own dataset with detrex models, all you need to do is to convert your dataset into coco format and register your dataset in config file as:

# coco_detr.py

from detectron2.data.datasets import register_coco_instances
register_coco_instances("my_dataset_train", {}, '/path/to/train.json', '/path/to/train/images')
register_coco_instances("my_dataset_test", {}, '/path/to/test.json', '/path/to/test/images')

Then modify the dataloader config:

dataloader.train = L(build_detection_train_loader)(
    dataset=L(get_detection_dataset_dicts)(names="my_dataset_train"),
    ...

dataloader.test = L(build_detection_test_loader)(
    dataset=L(get_detection_dataset_dicts)(names="my_dataset_test", filter_empty=False),
    ...