[Python] How to provide 4th argument for NM.SecretAgentOldGetSecretsFunc in NM 1.0 when...

I'm using Network Manager (NM 1.0) from PyGObject to create a widget that can show and connect to a network. I created a subclass of NM.SecretAgentOld to provide passwords to NM, basically I just overwrite the virtual method

def do_get_secrets(
self,
connection,
connection_path,
setting_name,
hints,
flags,
callback,
*callback_data
):

<after retrieving the password>

<convert password to GLib.Variant>

callback(self, connection, password, None)


And after retrieving the password I simply call the callback provided by NM. However callback (or more specifically NM.SecretAgentOldGetSecretsFunc type) takes 4th argument as a GLib.Error in case of any error. But it doesn't mention what to use when there's no error and using None raises a type error (it says argument 3 doesn't allow `None` type).

How can I fix this?

N.B: The code from the official Network Manager's python example secret-agent.py (gitlab) also shows type error.

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