def METHOD_NAME(client):
    from optimade.models.optimade_json import DataType
    format_value_fn = ImplementationValidator._format_test_value
    assert format_value_fn(["Ag", "Ba", "Ca"], DataType.LIST, "HAS") == '"Ag"'
    assert (
        format_value_fn(["Ag", "Ba", "Ca"], DataType.LIST, "HAS ANY")
        == '"Ag","Ba","Ca"'
    )
    assert format_value_fn([6, 1, 4], DataType.LIST, "HAS ALL") == "1,4,6"
    assert format_value_fn("test value", DataType.STRING, "CONTAINS") == '"test value"'
    assert format_value_fn(5, DataType.INTEGER, "=") == 5