text: _base_ = [
      '../_base_/models/mask_rcnn_r50_fpn.py',
      '../_base_/datasets/coco_instance.py',
      '../_base_/schedules/schedule_1x.py', '../_base_/default_runtime.py'
  ]
  
  model = dict(
      pretrained=None,
      backbone=dict(norm_cfg=dict(type='BN', requires_grad=False)),
      roi_head=dict(
          bbox_head=dict(type='Shared4Conv1FCBBoxHead', conv_out_channels=256)))
  
  # specify where the direct pre-trained model
  load_from = 'work_dirs/mask_rcnn_r50_fpn_direct_pretrain_1x_coco/epoch_12.pth'