def get_email_html_body(self):
        try:
            return self._get_email_field('email_html_body_tmpl', 'get_email_html_body')
        except ImproperlyConfigured:
            return None
Your class must define an `get_email_html_body` attribute
dataset/ETHPy150Open Nomadblue/django-nomad-notifier/notifier/models.py/NotificationMixin.get_email_html_body