pengyin

@YoungXIAO13 Hi, I am wondering if the [filter class function](https://github.com/YoungXIAO13/FewShotDetection/blob/b703ae7e341e1790923c6a910a6572fe2510b1f2/lib/roi_data_layer/roidb.py#L133) could guarantee that there will be 3K base instances in the query data, since it will add all the base...