code: def test_is_none_raises_error_when_field_does_not_exist(self) -> None:
      self.card.field("field2").set(None)
  
      with pytest.raises(
          AssetCardFieldNotFoundError,
          match=r"^The asset card 'test-card' must have a field named 'field2.sub_field2'\.$",
      ):
          self.card.field("field2").field("sub_field2").is_none()
  
imports: from os import PathLike
  from pathlib import Path
  import pytest
  from fairseq2.assets import AssetCard, AssetCardError, AssetCardFieldNotFoundError
label_desc: Use image node_id 4 for calling the TestAssetCard obj's underlying member method code with example usage: obj.test_is_none_raises_error_when_field_does_not_exist() without return types