Ensure Customuser is being used in Django App

I have a problem with implementing CustomUser in a Django App.

My project is called "VendorManagement".

My app is "VMP".

In settings, I have AUTH_USER_MODEL = 'VMP.CustomUser' set.

Here is my CustomUser Model:

from django.db import models
from django.conf import settings
from django.contrib.auth.models import User, AbstractUser
from django.utils.timezone import timedelta, now
from django.core.exceptions import ValidationError

# File validation function
def validate_file_type(value):
    allowed_types = ["application/pdf", "application/msword", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"]
    if value.content_type not in allowed_types:
        raise ValidationError("Only PDF and Word documents are allowed.")

class CustomUser(AbstractUser):
    ROLE_CHOICES = [
        ('vendor', 'Vendor'),
        ('customer', 'Customer'),
        ('admin', 'Admin'),
    ]
    role = models.CharField(max_length=20, choices=ROLE_CHOICES, default='customer')
    groups = models.ManyToManyField("auth.Group", related_name="custom_user_groups", blank=True)
    user_permissions = models.ManyToManyField("auth.Permission", related_name="custom_user_permissions", blank=True)

    def is_vendor(self):
        return self.role == "vendor"

    def is_customer(self):
        return self.role == "customer"

    def is_admin(self):
        return self. Role == "admin"

Here is my views:

from django.contrib.auth import get_user_model
from .models import *

# Get custom User model
CustomUser = get_user_model()

class RFPViewSet(viewsets.ModelViewSet):
    serializer_class = RFPSerializer

    def get_queryset(self):
        """Vendors see active RFPs, Customers see expired ones"""
        userid = self.request.user.id

        # Ensure user is fetched correctly as CustomUser
        user_instance = CustomUser.objects.filter(id=user.id).first()

        if user_instance.is_vendor():
            return RFP.objects.filter(is_expired=False, is_active=True)
        elif user_instance.is_customer():
            return RFP.objects.filter(customer=user_instance, is_expired=True)
        return RFP.objects.none()

The problme3 i that while the model does include is_customer() and is_vendor(), the functions are NOT found in the ViewSet code.

it says that the functions are not visible. In my IDE, it says that my type of variable is "AbstractUser" and not "CustomUser".

how do I fix this? THanks

class RFPViewSet(viewsets.ModelViewSet):
    serializer_class = RFPSerializer

    def get_queryset(self):
        """Vendors see active RFPs, Customers see expired ones"""
        user = self.request.user

        # No need to fetch as user is already a Custom User

        if user.is_vendor():
            return RFP.objects.filter(is_expired=False, is_active=True)
        elif user.is_customer():
            return RFP.objects.filter(customer=user_instance, is_expired=True)
        return RFP.objects.none()

    def is_admin(self):
        return self. Role == "admin"