def test_immutable_grammar(self):
        grammar = Grammar(r"""
            foo = 'bar'
        """)

        def mod_grammar(grammar):
            grammar['foo'] = 1
        assert_raises(TypeError, mod_grammar, [grammar])

        def mod_grammar(grammar):
            new_grammar = Grammar(r"""
                baz = 'biff'
            """)
            grammar.update(new_grammar)
        assert_raises(AttributeError, mod_grammar, [grammar])
List the snapshots of the given filesystem.
dataset/ETHPy150Open erikrose/parsimonious/parsimonious/tests/test_grammar.py/GrammarTests.test_immutable_grammar--crossover with--dataset/ETHPy150Open ClusterHQ/flocker/flocker/volume/filesystems/zfs.py/_list_snapshots