If you want to return the writeoff move.line which is to be reconciled follow the following code .

 return writeoff_move.line_ids.filtered(lambda r: r.account_id == self[0].account_id)

    @api.multi
    def remove_move_reconcile(self):
        """ Undo a reconciliation """
        if not self:
            return True
        rec_move_ids = self.env['account.partial.reconcile']
        for account_move_line in self:
            rec_move_ids += account_move_line.matched_debit_ids
            rec_move_ids += account_move_line.matched_credit_ids
        return rec_move_ids.unlink()


    @api.model
    def create(self, vals, apply_taxes=True):
        """ :param apply_taxes: set to False if you don't want vals['tax_ids'] to result in the creation of move lines for taxes and eventual
                adjustment of the line amount (in case of a tax included in price). This is useful for use cases where you don't want to
                apply taxes in the default fashion (eg. taxes). You can also pass 'dont_create_taxes' in context.

            :context's key `check_move_validity`: check data consistency after move line creation. Eg. set to false to disable verification that the move
                debit-credit == 0 while creating the move lines composing the move.

        """
        AccountObj = self.env['account.account']
        MoveObj = self.env['account.move']
        context = dict(self._context or {})
        amount = vals.get('debit', 0.0) - vals.get('credit', 0.0)

        if vals.get('move_id', False):
            move = MoveObj.browse(vals['move_id'])
            if move.date and not vals.get('date'):
                vals['date'] = move.date
        if ('account_id' in vals) and AccountObj.browse(vals['account_id']).deprecated:
            raise UserError(_('You cannot use deprecated account.'))
        if 'journal_id' in vals and vals['journal_id']:
            context['journal_id'] = vals['journal_id']
        if 'date' in vals and vals['date']:
            context['date'] = vals['date']
        if ('journal_id' not in context) and ('move_id' in vals) and vals['move_id']:
            m = MoveObj.browse(vals['move_id'])
            context['journal_id'] = m.journal_id.id
            context['date'] = m.date
        #we need to treat the case where a value is given in the context for period_id as a string
        if not context.get('journal_id', False) and context.get('search_default_journal_id', False):
            context['journal_id'] = context.get('search_default_journal_id')
        if 'date' not in context:
            context['date'] = fields.Date.context_today(self)
        move_id = vals.get('move_id', False)
        journal = self.env['account.journal'].browse(context['journal_id'])
        vals['journal_id'] = vals.get('journal_id') or context.get('journal_id')
        vals['date'] = vals.get('date') or context.get('date')
        vals['date_maturity'] = vals.get('date_maturity') if vals.get('date_maturity') else vals['date']
        if not move_id:
            if not vals.get('move_id', False):
                if journal.sequence_id:
                    #name = self.pool.get('ir.sequence').next_by_id(cr, uid, journal.sequence_id.id)
                    v = {
                        'date': vals.get('date', time.strftime('%Y-%m-%d')),
                        'journal_id': context['journal_id']
                    }
                    if vals.get('ref', ''):
                        v.update({'ref': vals['ref']})
                    move_id = MoveObj.with_context(context).create(v)
                    vals['move_id'] = move_id.id
                else:
                    raise UserError(_('Cannot create an automatic sequence for this piece.\nPut a sequence in the journal definition for automatic numbering or create a sequence manually for this piece.'))
        ok = not (journal.type_control_ids or journal.account_control_ids)
        if ('account_id' in vals):
            account = AccountObj.browse(vals['account_id'])
            if journal.type_control_ids:
                type = account.user_type_id
                for t in journal.type_control_ids:
                    if type.code == t.code:
                        ok = True
                        break
            if journal.account_control_ids and not ok:
                for a in journal.account_control_ids:
                    if a.id == vals['account_id']:
                        ok = True
                        break
            # Automatically convert in the account's secondary currency if there is one and
            # the provided values were not already multi-currency
            if account.currency_id and 'amount_currency' not in vals and account.currency_id.id != account.company_id.currency_id.id:
                vals['currency_id'] = account.currency_id.id
                ctx = {}
                if 'date' in vals:
                    ctx['date'] = vals['date']
                vals['amount_currency'] = account.company_id.currency_id.with_context(ctx).compute(amount, account.currency_id)
        if not ok:
            raise UserError(_('You cannot use this general account in this journal, check the tab \'Entry Controls\' on the related journal.'))

        # Create tax lines
        tax_lines_vals = []
        if apply_taxes and not context.get('dont_create_taxes') and vals.get('tax_ids'):
            # Get ids from triplets : https://www.odoo.com/documentation/master/reference/orm.html#openerp.models.Model.write
            tax_ids = [tax['id'] for tax in self.resolve_2many_commands('tax_ids', vals['tax_ids']) if tax.get('id')]
            # Since create() receives ids instead of recordset, let's just use the old-api bridge
            taxes = self.env['account.tax'].browse(tax_ids)
            currency = self.env['res.currency'].browse(vals.get('currency_id'))
            res = taxes.compute_all(amount,
                currency, 1, vals.get('product_id'), vals.get('partner_id'))
            # Adjust line amount if any tax is price_include
            if abs(res['total_excluded']) < abs(amount):
                if vals['debit'] != 0.0: vals['debit'] = res['total_excluded']
                if vals['credit'] != 0.0: vals['credit'] = -res['total_excluded']
                if vals.get('amount_currency'):
                    vals['amount_currency'] = self.env['res.currency'].browse(vals['currency_id']).round(vals['amount_currency'] * (amount / res['total_excluded']))
            # Create tax lines
            for tax_vals in res['taxes']:
                account_id = (amount > 0 and tax_vals['account_id'] or tax_vals['refund_account_id'])
                if not account_id: account_id = vals['account_id']
                tax_lines_vals.append({
                    'account_id': account_id,
                    'name': vals['name'] + ' ' + tax_vals['name'],
                    'tax_line_id': tax_vals['id'],
                    'move_id': vals['move_id'],
                    'date': vals['date'],
                    'partner_id': vals.get('partner_id'),
                    'ref': vals.get('ref'),
                    'statement_id': vals.get('statement_id'),
                    'debit': tax_vals['amount'] > 0 and tax_vals['amount'] or 0.0,
                    'credit': tax_vals['amount'] < 0 and -tax_vals['amount'] or 0.0,
                })

        new_line = super(AccountMoveLine, self).create(vals)
        for tax_line_vals in tax_lines_vals:
            # TODO: remove .with_context(context) once this context nonsense is solved
            self.with_context(context).create(tax_line_vals)

        if self._context.get('check_move_validity', True):
            move = MoveObj.browse(vals['move_id'])
            move.with_context(context)._post_validate()

        return new_line

    @api.multi
    def unlink(self):
        self._update_check()
        move_ids = set()
        for line in self:
            if line.move_id.id not in move_ids:
                move_ids.add(line.move_id.id)
        result = super(AccountMoveLine, self).unlink()
        if self._context.get('check_move_validity', True) and move_ids:
            self.env['account.move'].browse(list(move_ids))._post_validate()
        return result

    @api.multi
    def write(self, vals):
        if vals.get('tax_line_id') or vals.get('tax_ids'):
            raise UserError(_('You cannot change the tax, you should remove and recreate lines.'))
        if ('account_id' in vals) and self.env['account.account'].browse(vals['account_id']).deprecated:
            raise UserError(_('You cannot use deprecated account.'))
        if any(key in vals for key in ('account_id', 'journal_id', 'date', 'move_id', 'debit', 'credit', 'amount_currency', 'currency_id')):
            self._update_check()
        #when we set the expected payment date, log a note on the invoice_id related (if any)
        if vals.get('expected_pay_date') and self.invoice_id:
            msg = _('New expected payment date: ') + vals['expected_pay_date'] + '.\n' + vals.get('internal_note', '')
            self.invoice_id.message_post(body=msg) #TODO: check it is an internal note (not a regular email)!
        #when making a reconciliation on an existing liquidity journal item, mark the payment as reconciled
        if 'statement_id' in vals and self.payment_id:
            # In case of an internal transfer, there are 2 liquidity move lines to match with a bank statement
            if all(line.statement_id for line in self.payment_id.move_line_ids.filtered(lambda r: r.id != self.id and r.account_id.internal_type=='liquidity')):
                self.payment_id.state = 'reconciled'

        result = super(AccountMoveLine, self).write(vals)
        if self._context.get('check_move_validity', True):
            move_ids = set()
            for line in self:
                if line.move_id.id not in move_ids:
                    move_ids.add(line.move_id.id)
            self.env['account.move'].browse(list(move_ids))._post_validate()
        return result