'The initial value for an optional field can be set to ``None`` by
passing ``None`` to the ``initial`` parameter.'

@given(PYRSISTENT_STRUCT)
def test_none_initial_value(self, klass):

    initial = None
    class Record(klass, ):
        value = pmap_field(int, int, optional=True, initial=initial)
    assert (Record() == Record(value=initial))
