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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 sepa_debit(self, account: SEPAAccount, pain_message: str, multiple=False, cor1=False, control_sum=None, currency='EUR', book_as_single=False, pain_descriptor='urn:iso:std:iso:20022:tech:xsd:pain.008.003.01'):
 """ Custom SEPA debit. :param account: SEPAAccount to send the debit from. :param pain_message: SEPA PAIN message containing the debit details. :param multiple: Whether this message contains multiple debits. :param cor1: Whether to use COR1 debit (lead time reduced to 1 day) :param control_sum: Sum of all debits (required if there are multiple) :param currency: Debit currency :param book_as_single: Kindly ask the bank to put multiple transactions as separate lines on the bank statement (defaults to ``False``) :param pain_descriptor: URN of the PAIN message schema used. Defaults to ``urn:iso:std:iso:20022:tech:xsd:pain.008.003.01``. :return: Returns either a NeedRetryResponse or TransactionResponse (with data['task_id'] set, if available) """


        with self._get_dialog() as dialog:
            if multiple:
                if cor1:
                    command_candidates = (HKDMC1, )
                else:
                    command_candidates = (HKDME1, HKDME2)
            else:
                if cor1:
                    command_candidates = (HKDSC1, )
                else:
                    command_candidates = (HKDSE1, HKDSE2)

            hidxxs, hkdxx = self._find_highest_supported_command(
                *command_candidates,
                return_parameter_segment=True
            )

            seg = hkdxx(
                account=hkdxx._fields['account'].type.from_sepa_account(account),
                sepa_descriptor=pain_descriptor,
                sepa_pain_message=pain_message.encode(),
            )

            if multiple:
                if hidxxs.parameter.sum_amount_required and control_sum is None:
                    raise ValueError("Control sum required.")
                if book_as_single and not hidxxs.parameter.single_booking_allowed:
                    raise FinTSUnsupportedOperation("Single booking not allowed by bank.")

                if control_sum:
                    seg.sum_amount.amount = control_sum
                    seg.sum_amount.currency = currency

                if book_as_single:
                    seg.request_single_booking = True

            return self._send_with_possible_retry(dialog, seg, self._continue_sepa_debit)