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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def serialize(self) -> str: """ Dump current object to a JSON-compatible dictionary. :return: dict representation of current DIDDoc """


        return {
            '@context': DIDDoc.CONTEXT,
            'id': canon_ref(self.did, self.did),
            'publicKey': [pubkey.to_dict() for pubkey in self.pubkey.values()],
            'authentication': [{
                'type': pubkey.type.authn_type,
                'publicKey': canon_ref(self.did, pubkey.id)
            } for pubkey in self.pubkey.values() if pubkey.authn],
            'service': [service.to_dict() for service in self.service.values()]
        }