class_docstr: Bbox head used in Double-Head R-CNN
  
  .. code-block:: none
  
                                        /-> cls
                    /-> shared convs ->
                                        \-> reg
      roi features
                                        /-> cls
                    \-> shared fc    ->
                                        \-> reg
docstr: Add the fc branch which consists of a sequential of fc layers.
docstr_tok: ["Add","the","fc","branch","which","consists","of","a","sequential","of","fc","layers","."]
code: def _add_fc_branch(self):
      """Add the fc branch which consists of a sequential of fc layers."""
      branch_fcs = nn.ModuleList()
      for i in range(self.num_fcs):
          fc_in_channels = (
              self.in_channels * self.roi_feat_area
              if i == 0
              else self.fc_out_channels
          )
          branch_fcs.append(
              nn.Linear(fc_in_channels, self.fc_out_channels)
          )
      return branch_fcs
  
file_path: insightface/detection/scrfd/mmdet/models/roi_heads/bbox_heads/double_bbox_head.py
imports: import torch.nn
  from mmcv.cnn import ConvModule, normal_init, xavier_init
  from mmdet.models.backbones.resnet import Bottleneck
  from mmdet.models.builder import HEADS
  from .bbox_head import BBoxHead
label_desc: Use image node_id 3 for calling the DoubleConvFCBBoxHead obj's underlying member method code with example usage: obj._add_fc_branch() and returns: branch_fcs