Runtime error: Uninitialized attribute _s (alt/test_json_deserialization_plain_alt2.nit:22)
# JSON: {"__class": "MyClass", "i": 123, "o": null}
# Errors: 'Deserialization Error: attribute `MyClass::s` missing from JSON object', 'Deserialization Error: attribute `MyClass::f` missing from JSON object', 'Deserialization Error: attribute `MyClass::a` missing from JSON object'