def METHOD_NAME():
    """Test that the usage of use_legacy_supplementaries is deprecated."""
    msg = "use_legacy_supplementaries"
    session = CFG.start_session('my_session')
    with pytest.warns(ESMValCoreDeprecationWarning, match=msg):
        session.update({'use_legacy_supplementaries': False})
    assert session['use_legacy_supplementaries'] is False