code: def test_path_attr_unknown():
      path = ObjectPath.root().attr(None)
      assert isinstance(path, object_path.UnknownAttributeAccessPath)
      assert str(path) == "<root>.<unknown attribute>"
      assert len(path) == 2
      assert path.parent == ObjectPath.root()
  
file_path: tvm/tests/python/ir/test_object_path.py
imports: import pytest
  import tvm
  from tvm.runtime import object_path
  from tvm.runtime.object_path import ObjectPath
label_desc: Use image node_id 4 for calling a global function with example usage: test_path_attr_unknown() without return types