<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 async def build_auth_rule_request(submitter_did: str, txn_type: str, action: str, field: str, old_value: Optional[str], new_value: Optional[str], constraint: str) -> str: """ Builds a AUTH_RULE request. Request to change authentication rules for a ledger transaction. :param submitter_did: DID of the submitter stored in secured Wallet. :param txn_type: ledger transaction alias or associated value. :param action: type of an action. Can be either "ADD" (to add a new rule) or "EDIT" (to edit an existing one). :param field: transaction field. :param old_value: (Optional) old value of a field, which can be changed to a new_value (mandatory for EDIT action). :param new_value: (Optional) new value that can be used to fill the field. :param constraint: set of constraints required for execution of an action in the following format: { constraint_id - <string> type of a constraint. Can be either "ROLE" to specify final constraint or "AND"/"OR" to combine constraints. role - <string> role of a user which satisfy to constrain. sig_count - <u32> the number of signatures required to execution action. need_to_be_owner - <bool> if user must be an owner of transaction. metadata - <object> additional parameters of the constraint. } can be combined by { 'constraint_id': <"AND" or "OR"> 'auth_constraints': [<constraint_1>, <constraint_2>] } Default ledger auth rules: https://github.com/hyperledger/indy-node/blob/master/docs/source/auth_rules.md More about AUTH_RULE request: https://github.com/hyperledger/indy-node/blob/master/docs/source/requests.md#auth_rule :return: Request result as json. """


    logger = logging.getLogger(__name__)
    logger.debug("build_auth_rule_request: >>> submitter_did: %r, txn_type: %r, action: %r, field: %r, "
                 "old_value: %r, new_value: %r, constraint: %r",
                 submitter_did,
                 txn_type,
                 action,
                 field,
                 old_value,
                 new_value,
                 constraint)

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

    c_submitter_did = c_char_p(submitter_did.encode('utf-8'))
    c_txn_type = c_char_p(txn_type.encode('utf-8'))
    c_action = c_char_p(action.encode('utf-8'))
    c_field = c_char_p(field.encode('utf-8'))
    c_old_value = c_char_p(old_value.encode('utf-8')) if old_value is not None else None
    c_new_value = c_char_p(new_value.encode('utf-8')) if new_value is not None else None
    c_constraint = c_char_p(constraint.encode('utf-8'))

    request_json = await do_call('indy_build_auth_rule_request',
                                 c_submitter_did,
                                 c_txn_type,
                                 c_action,
                                 c_field,
                                 c_old_value,
                                 c_new_value,
                                 c_constraint,
                                 build_auth_rule_request.cb)

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