def _create_service_invoice(self):
        pool = Pool()
        HealthService = pool.get('pathocytology.health_service')
        Invoice = pool.get('account.invoice')
        Party = pool.get('party.party')
        Journal = pool.get('account.journal')

        currency_id = Transaction().context.get('currency')

        service = self.record

        services = self.records

        # Invoice Lines
        invoice_lines = []

        for service in services:
            # Invoice Header
            if service.state == 'invoiced':
                raise ServiceAlreadyInvoiced(
                gettext('pathocytology_service.msg_service_already_invoiced'))

            party = service.invoice_to or service.patient.name

            sale_price_list = party.sale_price_list \
                if hasattr(party, 'sale_price_list') else None

            ctx = {
                'price_list': sale_price_list.id,
                'sale_date': date.today(),
                'currency': currency_id,
                'customer': party.id
            } if sale_price_list else {}

            journals = Journal.search([('type', '=', 'revenue')], limit=1)
            journal, = journals if journals else None

            party_address = Party.address_get(party, type='invoice')
            if not party_address:
                raise NoInvoiceAddress(
                    gettext('pathocytology_service.msg_no_invoice_address'))

            if not party.customer_payment_term:
                raise NoPaymentTerm(
                    gettext('pathocytology_service.msg_no_payment_term'))

            for seq, line in enumerate(service.service_line):
                if sale_price_list:
                    with Transaction().set_context(ctx):
                        unit_price = sale_price_list.compute(
                            party, line.product, line.product.list_price,
                            line.qty, line.product.default_uom)
                else:
                    unit_price = line.product.list_price

                invoice_lines.append({
                    'origin': f"{line}",
                    'product': line.product.id,
                    'description': line.desc,
                    'quantity': line.qty,
                    'account': line.product.template.account_revenue_used.id,
                    'unit': line.product.default_uom.id,
                    'unit_price': unit_price,
                    'sequence': seq + 1,
                    'taxes': [product_tax_line.id
                            for product_tax_line in line.product.customer_taxes_used
                            if line.to_invoice],

                })

        invoice = Invoice(
            description=service.desc,
            party=party.id,
            type='out',
            invoice_date=date.today(),
            account=party.account_receivable.id,
            company=service.company.id,
            journal=journal.id,
            invoice_address=party_address.id,
            reference=service.name,
            payment_term=party.customer_payment_term.id,
            lines=invoice_lines
        )
        invoice.save()
        invoices = [invoice]
        Invoice.update_taxes(invoices)

        # Change to invoiced the status on the service document.
        HealthService.write(services, {'state': 'invoiced', 'invoice': invoice.id})

        return invoice

    def do_open_(self, action):
        invoice = self._create_service_invoice()
        action['res_id'] = [invoice.id]
        return action, {}