mmdetection/configs/cascade_rcnn/cascade-rcnn_r101-caffe_fpn_1x_coco.py

_base_ = './cascade-rcnn_r50-caffe_fpn_1x_coco.py'
model = dict(
    backbone=dict(
        depth=101,
        init_cfg=dict(
            type='Pretrained',
            checkpoint='open-mmlab://detectron2/resnet101_caffe')))