code: def test_unet_fpn_backbones_small(model_name, param_groups_len):
      backbone_fn = getattr(models.fastai.unet.backbones, model_name)
      backbone = backbone_fn(pretrained=False)
  
      model = unet.model(img_size=64, num_classes=4, backbone=backbone)
      assert len(list(model.param_groups())) == param_groups_len
  
imports: import pytest
  from icevision.all import *
  from icevision.models.fastai import unet
label_desc: Use image node_id 3 for calling a global function with example usage: test_unet_fpn_backbones_small(model_name, param_groups_len) without return types