text: from .s3dg import S3D
  from .resnet_2d3d import r2d3d50
  
  def select_backbone(network, first_channel=3):
      param = {'feature_size': 1024}
      if network == 's3d':
          model = S3D(input_channel=first_channel)
      elif network == 's3dg':
          model = S3D(input_channel=first_channel, gating=True)
      elif network == 'r50':
          param['feature_size'] = 2048
          model = r2d3d50(input_channel=first_channel)
      else:
          raise NotImplementedError
  
      return model, param
  