code: def test_as_filename_works(self) -> None:
      value = self.card.field("field1").as_filename()
  
      assert value == "foo1"
  
imports: from os import PathLike
  from pathlib import Path
  import pytest
  from fairseq2.assets import AssetCard, AssetCardError, AssetCardFieldNotFoundError
label_desc: Use image node_id 20 for calling the TestAssetCard obj's underlying member method code with example usage: obj.test_as_filename_works() without return types