Is Python's code marshalling reversible?

Question

Consider the following script:

from marshal import dumps, loads


def square_fn(x):
    return x * x


def test_serialize_marshal():
    code_string = dumps(square_fn.__code__)
    code_string1 = dumps(loads(code_string))
    assert code_string == code_string1

Run in Python 3.6 with pytest.

This test is failing on my computer. Why is this so?

I am trying to serialize a Python function in a way that I can test, from its serialized representation, that the function is the same... This test suggests that this is not the case for marshal dumps/loads.

EDIT:

Interestingly, this test passes:

def test_serialize_marshal2():
    import types

    code = dumps(square_fn.__code__)
    ff = types.FunctionType(loads(code), globals())

    assert square_fn.__code__ == ff.__code__

which is what this answer tests. However, I do not want the equality of the Python object, but of the string.