Can you please fix line 149 and line 150 to use the correct self properties? This is what it currently has:

            'aud': audience or self.issuer,
            'sub': subject or self.issuer,

but since the constructor sets self.audience and self.subject, those are the values that should be used, like this:

            'aud': audience or self.audience,
            'sub': subject or self.subject,