code: def test_unknown_default_schema(self):
      with pytest.raises(ValueError, match="Unknown default data type"):
          validate_schema(
              nodes=["new"], schema={}, default_type="unknown"
          )
  
imports: from collections import OrderedDict
  import pytest
  from causalnex.structure import StructureModel
  from causalnex.structure.categorical_variable_mapper import VariableFeatureMapper, validate_schema
label_desc: Use image node_id 3 for calling the TestValidateSchema obj's underlying member method code with example usage: obj.test_unknown_default_schema() without return types