Verify proof as Verifier. Raise AbsentRevReg if a proof cites a revocation registry
        that does not exist on the distributed ledger.

        :param proof_req: proof request as Verifier creates, as per proof_req_json above
        :param proof: proof as HolderProver creates
        :return: json encoded True if proof is valid; False if not

async def verify_proof(self, proof_req: dict, proof: dict) -> str:
        """
        Verify proof as Verifier. Raise AbsentRevReg if a proof cites a revocation registry
        that does not exist on the distributed ledger.

        :param proof_req: proof request as Verifier creates, as per proof_req_json above
        :param proof: proof as HolderProver creates
        :return: json encoded True if proof is valid; False if not
        """

        LOGGER.debug('Verifier.verify_proof >>> proof_req: %s, proof: %s', proof_req, proof)

        s_id2schema = {}
        cd_id2cred_def = {}
        rr_id2rr_def = {}
        rr_id2rr = {}
        proof_ids = proof['identifiers']

        for proof_id in proof_ids:
            # schema
            s_id = proof_id['schema_id']
            if s_id not in s_id2schema:
                schema = json.loads(await self.get_schema(s_id))  # add to cache en passant
                if not schema:
                    LOGGER.debug(
                        'Verifier.verify_proof: <!< absent schema %s, proof req may be for another ledger',
                        s_id)
                    raise AbsentSchema(
                        'Absent schema {}, proof req may be for another ledger'.format(s_id))
                s_id2schema[s_id] = schema

            # cred def
            cd_id = proof_id['cred_def_id']
            if cd_id not in cd_id2cred_def:
                cred_def = json.loads(await self.get_cred_def(cd_id))  # add to cache en passant
                cd_id2cred_def[cd_id] = cred_def

            # rev reg def
            rr_id = proof_id['rev_reg_id']
            if not rr_id:
                continue

            rr_def_json = await self._get_rev_reg_def(rr_id)
            rr_id2rr_def[rr_id] = json.loads(rr_def_json)

            # timestamp
            timestamp = proof_id['timestamp']
            with REVO_CACHE.lock:
                revo_cache_entry = REVO_CACHE.get(rr_id, None)
                (rr_json, _) = await revo_cache_entry.get_state_json(self._build_rr_state_json, timestamp, timestamp)
                if rr_id not in rr_id2rr:
                    rr_id2rr[rr_id] = {}
                rr_id2rr[rr_id][timestamp] = json.loads(rr_json)

        rv = json.dumps(await anoncreds.verifier_verify_proof(
            json.dumps(proof_req),
            json.dumps(proof),
            json.dumps(s_id2schema),
            json.dumps(cd_id2cred_def),
            json.dumps(rr_id2rr_def),
            json.dumps(rr_id2rr)))

        LOGGER.debug('Verifier.verify_proof <<< %s', rv)
        return rv