User object has no attribute acl

Hi, @rafalp :
Can I ask question?

from django.contrib.auth import get_user_model
UserModel = get_user_model()
u = UserModel.objects.all().first()
> u.acl
> AttributeError:'User' object has no attribute 'acl'

but within user serializers,this user have acl attribute .

# ...\misago\users\serializers\user.py
class UserSerializer(serializers.ModelSerializer, MutableFields):
    ......
    acl = serializers.SerializerMethodField()

    def get_acl(self, obj):
        return obj.acl
# here the `obj` is user istance,am i right?

So my question is why u.acl get error,but obj.acl just fine.
Thank You!