Is it possible just loading random part of training dataset by "build_detection_train_loader"??

[yellowjs0304]

Hi, I'm new with detectron2, Please help me with this problem.

I have COCO format "train.json" about 70000 images.

Is it possible to load just a part of train set, like (500 random load or 1000 random load)...

I think this is not same with mapper's sampler.
( I understand the sampler works like "randomly select N images in every step or iteration" so in the end the model uses whole dataset. Is this right? )

I just want to use randomly selected 500 images from total train dataset in training.
Am I should modify the "train.json" file?