mmdetection/configs/dcnv2/faster-rcnn_r50-mdconv-group4-c3-c5_fpn_1x_coco.py

_base_ = '../faster_rcnn/faster-rcnn_r50_fpn_1x_coco.py'
model = dict(
    backbone=dict(
        dcn=dict(type='DCNv2', deform_groups=4, fallback_on_stride=False),
        stage_with_dcn=(False, True, True, True)))