code: def test_study_user_attrs() -> None:
      study = optuna.multi_objective.create_study(
          ["minimize", "maximize"]
      )
      assert study.user_attrs == {}
  
      study.set_user_attr("foo", "bar")
      assert study.user_attrs == {"foo": "bar"}
  
      study.set_user_attr("baz", "qux")
      assert study.user_attrs == {"foo": "bar", "baz": "qux"}
  
      study.set_user_attr("foo", "quux")
      assert study.user_attrs == {"foo": "quux", "baz": "qux"}
  
file_path: optuna/tests/multi_objective_tests/test_study.py
imports: from typing import List
  from typing import Tuple
  import uuid
  import _pytest.capture
  import pytest
  import optuna
  from optuna.study._study_direction import StudyDirection
  from optuna.testing.storages import StorageSupplier
label_desc: Use image node_id 5 for calling a global function with example usage: test_study_user_attrs() without return types