text: # encoding: utf-8
  """
  @author:  liaoxingyu
  @contact: sherlockliao01@gmail.com
  """
  
  from ...utils.registry import Registry
  
  BACKBONE_REGISTRY = Registry("BACKBONE")
  BACKBONE_REGISTRY.__doc__ = """
  Registry for backbones, which extract feature maps from images
  The registered object must be a callable that accepts two arguments:
  1. A :class:`detectron2.config.CfgNode`
  2. A :class:`detectron2.layers.ShapeSpec`, which contains the input shape specification.
  It must returns an instance of :class:`Backbone`.
  """
  
  
  def build_backbone(cfg):
      """
      Build a backbone from `cfg.MODEL.BACKBONE.NAME`.
      Returns:
          an instance of :class:`Backbone`
      """
  
      backbone_name = cfg.MODEL.BACKBONE.NAME
      backbone = BACKBONE_REGISTRY.get(backbone_name)(cfg)
      # print(backbone)
      return backbone
  