class_docstr: Implementation of Region Proposal Network.
class_docstr_tok: ["Implementation","of","Region","Proposal","Network","."]
docstr: Extract features.
  
  Args:
      img (torch.Tensor): Image tensor with shape (n, c, h ,w).
  
  Returns:
      list[torch.Tensor]: Multi-level features that may have
          different resolutions.
docstr_tok: ["Extract","features",".","Args",":","img","(","torch.Tensor",")",":","Image","tensor","with","shape","(","n",",","c",",","h",",","w",")",".","Returns",":","list","[","torch.Tensor","]",":","Multi-level","features","that","may","have","different","resolutions","."]
code: def extract_feat(self, img):
      """Extract features.
  
      Args:
          img (torch.Tensor): Image tensor with shape (n, c, h ,w).
  
      Returns:
          list[torch.Tensor]: Multi-level features that may have
              different resolutions.
      """
      x = self.backbone(img)
      if self.with_neck:
          x = self.neck(x)
      return x
  
file_path: insightface/detection/scrfd/mmdet/models/detectors/rpn.py
imports: import mmcv
  from mmcv.image import tensor2imgs
  from mmdet.core import bbox_mapping
  from ..builder import DETECTORS, build_backbone, build_head, build_neck
  from .base import BaseDetector
label_desc: Use image node_id 3 for calling the RPN obj's underlying member method code with example usage: obj.extract_feat(img) and returns: x