      MaxValueValidator, MinLengthValidator, MinValueValidator
  )
  from django.db import models
  from django.test import TestCase
  from django.utils import six
  
  from rest_framework import serializers
  from rest_framework.compat import postgres_fields, unicode_repr
  
  from .models import NestedForeignKeySource
 
</s> remove from rest_framework.compat import postgres_fields, unicode_repr
 </s> add from rest_framework.compat import postgres_fields </s> remove from rest_framework.compat import Mapping, unicode_repr
 </s> add from rest_framework.compat import Mapping </s> remove from __future__ import unicode_literals

 </s> add  </s> remove from django.utils import six
 </s> add  </s> remove from __future__ import unicode_literals

 </s> add 
      MaxValueValidator, MinLengthValidator, MinValueValidator
  )
  from django.db import models
  from django.test import TestCase

  
  from rest_framework import serializers
  from rest_framework.compat import postgres_fields, unicode_repr
  
  from .models import NestedForeignKeySource
keep keep keep keep replace keep keep keep keep keep
 Dropped Python 2 compatibility. (#6615)

Thanks to Jon Dufresne (@jdufresne) for review.

Co-authored-by: Asif Saif Uddin <auvipy@gmail.com>
Co-authored-by: Rizwan Mansuri <Rizwan@webbyfox.com> 
tests/test_model_serializer.py