Model class app_name.models.MyModel doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS

[lidyum]

python=3.8
django=3.1.5
djangorestframework=3.12.2

Using docker image and docker-compose file. Docker-compose file at the following.

my_api:
    container_name: 'my_api'
    build: .
    command: export DJANGO_SETTINGS_MODULE=core.settings &&
      python manage.py collectstatic --noinput &&
      python manage.py migrate --noinput &&
      architect partition --module my_app.models &&
      /start.sh"
    ports:
      - "8000:80"

architect command raise exception;

Traceback (most recent call last):
my_api            |   File "/usr/local/bin/architect", line 8, in <module>
my_api            |     sys.exit(main())
my_api            |   File "/usr/local/lib/python3.8/site-packages/architect/commands/__init__.py", line 93, in main
my_api            |     commands[command]['parser'].result(args.func(vars(args)))
my_api            |   File "/usr/local/lib/python3.8/site-packages/architect/commands/partition.py", line 26, in run
my_api            |     module_clss = filter(lambda obj: isinstance(obj, type), __import__(module, fromlist=module).__dict__.values())
my_api            |   File "/code/my_app/models.py", line 5, in <module>
my_api            |     class DepartmentModel(models.Model):
my_api            |   File "/usr/local/lib/python3.8/site-packages/django/db/models/base.py", line 113, in __new__
my_api            |     raise RuntimeError(
my_api            | RuntimeError: Model class my_app.models.DepartmentModel doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

structure is standart
my_app
-> models.py
core
-> settings.py

settings.py

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',

    "django_filters",
    "rest_framework",
    "polymorphic",
    "django_cleanup",
    "drf_yasg",

    "my_app"
]

models.py

class DepartmentModel(models.Model):
    name = models.CharField(max_length=255, unique=True, verbose_name=_('Department'))

    class Meta:
        verbose_name = _('Department')
        verbose_name_plural = _('Departments')
        #app_label = 'my_app'

    def __str__(self):
        return self.name

if I add app_label in to Meta class, is working, otherwise raise exception. WHY!!