'Notification' object has no attribute 'send'

I have created email notification for issue creation on “New” but when new issue is registered following error is thrown. Anyone please help me with this.

‘Notification’ object has no attribute ‘send’

Traceback (most recent call last):
File “apps/frappe/frappe/email/doctype/notification/notification.py”, line 454, in evaluate_alert
alert.send(doc)
AttributeError: ‘Notification’ object has no attribute ‘send’