Builds a GET_REVOC_REG_DELTA request. Request to get the delta of the accumulated state of the Revocation Registry.
    The Delta is defined by from and to timestamp fields.
    If from is not specified, then the whole state till to will be returned.

    :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 from_: Requested time represented as a total number of seconds from Unix Epoch
    :param to: Requested time represented as a total number of seconds from Unix Epoch
    :return: Request result as json.

async def build_get_revoc_reg_delta_request(submitter_did: Optional[str],
                                            revoc_reg_def_id: str,
                                            from_: Optional[int],
                                            to: int) -> str:
    """
    Builds a GET_REVOC_REG_DELTA request. Request to get the delta of the accumulated state of the Revocation Registry.
    The Delta is defined by from and to timestamp fields.
    If from is not specified, then the whole state till to will be returned.

    :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 from_: Requested time represented as a total number of seconds from Unix Epoch
    :param to: 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_delta_request: >>> submitter_did: %r, revoc_reg_def_id: %r, from: %r, to: %r",
                 submitter_did, revoc_reg_def_id, from_, to)

    if not hasattr(build_get_revoc_reg_delta_request, "cb"):
        logger.debug("build_get_revoc_reg_delta_request: Creating callback")
        build_get_revoc_reg_delta_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_from = c_int64(from_) if from_  else -1
    c_to = c_int64(to)

    request_json = await do_call('indy_build_get_revoc_reg_delta_request',
                                 c_submitter_did,
                                 c_revoc_reg_def_id,
                                 c_from,
                                 c_to,
                                 build_get_revoc_reg_delta_request.cb)

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