LVIS-92i Train Code issue (?)

[paolopertino]

Hello,
I think there is an issue on LVIS-92i dataloader when it is used in train mode. Specifically at line 71 train_cat_ids = list(train_anno.keys()) there is no check if the categories have at least nshot samples (this is instead done in case of validation).

Proposed fix:

train_cat_ids = [i for i in list(train_anno.keys()) if len(train_anno[i]) > self.shot]