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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:
 async def build_get_revoc_reg_request(submitter_did: Optional[str], revoc_reg_def_id: str, timestamp: int) -> str: """ Builds a GET_REVOC_REG request. Request to get the accumulated state of the Revocation Registry by ID. The state is defined by the given timestamp. :param submitter_did: (Optional) DID of the read request sender (if not provided then default Libindy DID will be used). :param revoc_reg_def_id: ID of the corresponding Revocation Registry Definition in ledger. :param timestamp: Requested time represented as a total number of seconds from Unix Epoch :return: Request result as json. """


    logger = logging.getLogger(__name__)
    logger.debug("build_get_revoc_reg_request: >>> submitter_did: %r, revoc_reg_def_id: %r, timestamp: %r",
                 submitter_did, revoc_reg_def_id, timestamp)

    if not hasattr(build_get_revoc_reg_request, "cb"):
        logger.debug("build_get_revoc_reg_request: Creating callback")
        build_get_revoc_reg_request.cb = create_cb(CFUNCTYPE(None, c_int32, c_int32, c_char_p))

    c_submitter_did = c_char_p(submitter_did.encode('utf-8')) if submitter_did is not None else None
    c_revoc_reg_def_id = c_char_p(revoc_reg_def_id.encode('utf-8'))
    c_timestamp = c_int64(timestamp)

    request_json = await do_call('indy_build_get_revoc_reg_request',
                                 c_submitter_did,
                                 c_revoc_reg_def_id,
                                 c_timestamp,
                                 build_get_revoc_reg_request.cb)

    res = request_json.decode()
    logger.debug("build_get_revoc_reg_request: <<< res: %r", res)
    return res