Django: AttributeError - type object has no attribute '_meta'

Question

I'm working on a Django project, and I encountered an AttributeError when running python manage.py makemigrations. The error message I'm getting is:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    main()
  File "manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  ...
  File "django_filters/filterset.py", line 325, in get_filters
    field = get_model_field(cls._meta.model, field_name)
  ...
AttributeError: type object 'AppUserManager' has no attribute '_meta'. Did you mean: 'Meta'?

I have a AppUserManager model in my Django project, and I'm trying to create a filter using django-filter. It seems like there's an issue with the model's metadata.

I have already checked that the model has a class Meta definition, and it seems to be correct.

Here's my models.py:

from django.db import models


class AppUserManager(BaseUserManager):

    def _create_user(self, email, password, **extra_fields):
        """
        Creates and saves a User with the given email and password.
        """
        if not email:
            raise ValueError('The given email must be set')
        email = self.normalize_email(email)
        user = self.model(email=email, **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_user(self, email, password=None, **extra_fields):
        extra_fields.setdefault('is_superuser', False)
        return self._create_user(email, password, **extra_fields)

    def create_superuser(self, email, password, **extra_fields):

        extra_fields.setdefault('is_superuser', True)
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_active', True)

        extra_fields.pop('tag')
        if extra_fields.get('is_superuser') is not True:
            raise ValueError('Superuser must have is_superuser=True.')

        return self._create_user(email, password, **extra_fields)
    class Meta:
        db_table = 'app_user_manager'

And here's my filters.py:

import django_filters
from .models import AppUserManager

class AppUserManagerFilter(django_filters.FilterSet):
    class Meta:
        model = AppUserManager
        fields = {
            'email': ['exact', 'icontains'],
            'is_superuser': ['exact'],
            'is_staff': ['exact'],
            'is_active': ['exact'],
        }

I'm not sure what's causing this issue and how to resolve it. Can someone help me understand what's going wrong and how to fix it? Thank you!

What I've Tried:

1. Checked the models.py file to ensure that the AppUserManager model has a valid class Meta definition.
2. Verified that I'm using the correct import statement for the AppUserManager model in my filters.py.
3. Made sure that there are no typos or syntax errors in my model and filter class definitions.
4. Checked if there are any circular import issues between different parts of my Django project (for example, circular imports between models and filters).
5. Looked at other parts of my code that might be related to the issue.

What I Was Expecting:

I was expecting that by defining the class Meta in my models.py and using it in my filters.py, I should be able to create a filter for the AppUserManager model using django-filter. My expectation was that the filter would work without any AttributeError related to _meta.