code: def test_fastai_train(camvid_ds, backbone):
      train_ds, valid_ds = camvid_ds
      train_dl = segformer.train_dl(
          train_ds, batch_size=4, num_workers=0, shuffle=False
      )
      valid_dl = segformer.valid_dl(
          valid_ds, batch_size=1, num_workers=0, shuffle=False
      )
      model = segformer.model(
          num_classes=32, backbone=backbone(pretrained=True)
      )
  
      learn = segformer.learner(dls=[train_dl, valid_dl], model=model)
  
      learn.fine_tune(1, 1e-4)
  
imports: import pytest
  from icevision.all import *
  from icevision.models.mmseg.models.segformer.backbones import *
  from icevision.models.mmseg.models import *
label_desc: Use image node_id 1 for calling a global function with example usage: test_fastai_train(camvid_ds, backbone) without return types