<filename>howl/apps.py
from django.apps import AppConfig
from django.utils.translation import gettext_lazy as _


class DjangoHowlConfig(AppConfig):
    name = "howl"
    verbose_name = _("Howl")

    def ready(self):
        from howl.models import do_operator_setup

        model = self.get_model("Observer")
        do_operator_setup(model)

<filename>howl/apps.py
from django.apps import AppConfig
from django.utils.translation import gettext_lazy as _


class DjangoHowlConfig(AppConfig):
    name = "howl"
    verbose_name = _("Howl")

    def ready(self):
        from howl.models import do_operator_setup

        model = self.get_model("Observer")
        do_operator_setup(model)
