Error:

Odoo Server Error

Traceback (most recent call last):

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\http.py", line 624, in _handle_exception

    return super(JsonRequest, self)._handle_exception(exception)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\http.py", line 310, in _handle_exception

    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\tools\pycompat.py", line 14, in reraise

    raise value

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\http.py", line 669, in dispatch

    result = self._call_function(**self.params)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\http.py", line 350, in _call_function

    return checked_call(self.db, *args, **kwargs)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\service\model.py", line 94, in wrapper

    return f(dbname, *args, **kwargs)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\http.py", line 339, in checked_call

    result = self.endpoint(*a, **kw)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\http.py", line 915, in __call__

    return self.method(*args, **kw)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\http.py", line 515, in response_wrap

    response = f(*args, **kw)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\addons\web\controllers\main.py", line 1326, in call_button

    action = self._call_kw(model, method, args, kwargs)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\addons\web\controllers\main.py", line 1314, in _call_kw

    return call_kw(request.env[model], method, args, kwargs)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\api.py", line 387, in call_kw

    result = _call_kw_multi(method, model, args, kwargs)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\api.py", line 374, in _call_kw_multi

    result = method(recs, *args, **kwargs)

  File "<decorator-gen-60>", line 2, in button_immediate_install

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\addons\base\models\ir_module.py", line 72, in check_and_log

    return method(self, *args, **kwargs)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\addons\base\models\ir_module.py", line 463, in button_immediate_install

    return self._button_immediate_function(type(self).button_install)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\addons\base\models\ir_module.py", line 573, in _button_immediate_function

    modules.registry.Registry.new(self._cr.dbname, update_module=True)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\modules\registry.py", line 86, in new

    odoo.modules.load_modules(registry._db, force_demo, status, update_module)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\modules\loading.py", line 423, in load_modules

    loaded_modules, update_module, models_to_check)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\modules\loading.py", line 315, in load_marked_modules

    perform_checks=perform_checks, models_to_check=models_to_check

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\modules\loading.py", line 182, in load_module_graph

    load_openerp_module(package.name)

  File "D:\odoo_doymaint\Odoo 13.0\server\odoo\modules\module.py", line 376, in load_openerp_module

    __import__('odoo.addons.' + module_name)

  File "d:\odoo_doymaint\odoo 13.0\server\addons\os_helpdesk\__init__.py", line 2, in <module>

    from . import models

  File "d:\odoo_doymaint\odoo 13.0\server\addons\os_helpdesk\models\__init__.py", line 2, in <module>

    from . import helpdesk_ticket

  File "d:\odoo_doymaint\odoo 13.0\server\addons\os_helpdesk\models\helpdesk_ticket.py", line 5, in <module>

    class HelpdeskTicket(models.Model):

  File "d:\odoo_doymaint\odoo 13.0\server\addons\os_helpdesk\models\helpdesk_ticket.py", line 50, in HelpdeskTicket

    @api.multi

AttributeError: module 'odoo.api' has no attribute 'multi'