content: from alphaction.modeling import registry
  from . import slowfast, i3d
  
  @registry.BACKBONES.register("Slowfast-Resnet50")
  @registry.BACKBONES.register("Slowfast-Resnet101")
  def build_slowfast_resnet_backbone(cfg):
      model = slowfast.SlowFast(cfg)
      return model
  
  @registry.BACKBONES.register("I3D-Resnet50")
  @registry.BACKBONES.register("I3D-Resnet101")
  @registry.BACKBONES.register("I3D-Resnet50-Sparse")
  @registry.BACKBONES.register("I3D-Resnet101-Sparse")
  def build_i3d_resnet_backbone(cfg):
      model = i3d.I3D(cfg)
      return model
  
  def build_backbone(cfg):
      assert cfg.MODEL.BACKBONE.CONV_BODY in registry.BACKBONES, \
          "cfg.MODEL.BACKBONE.CONV_BODY: {} are not registered in registry".format(
              cfg.MODEL.BACKBONE.CONV_BODY
          )
      return registry.BACKBONES[cfg.MODEL.BACKBONE.CONV_BODY](cfg)