          # Now we have all the field names that have uniqueness constraints
          # applied, we can add the extra 'required=...' or 'default=...'
          # arguments that are appropriate to these fields, or add a `HiddenField` for it.
          for unique_constraint_name in unique_constraint_names:
              # Get the model field that is refered too.
              unique_constraint_field = model._meta.get_field(unique_constraint_name)
  
              if getattr(unique_constraint_field, 'auto_now_add', None):
                  default = CreateOnlyDefault(timezone.now)
              elif getattr(unique_constraint_field, 'auto_now', None):
 
</s> remove         # `fields` is evalutated lazily. We do this to ensure that we don't
 </s> add         # `fields` is evaluated lazily. We do this to ensure that we don't </s> remove             # a 404 reponse.
 </s> add             # a 404 response. </s> remove         # The suffix initkwarg is reserved for identifing the viewset type
 </s> add         # The suffix initkwarg is reserved for identifying the viewset type </s> remove class IneritedModelSerializationTests(TestCase):
 </s> add class InheritedModelSerializationTests(TestCase): </s> remove         validtors should not be added for that field.
 </s> add         validators should not be added for that field.
            # Get the model field that is referred too.
          # Now we have all the field names that have uniqueness constraints
          # applied, we can add the extra 'required=...' or 'default=...'
          # arguments that are appropriate to these fields, or add a `HiddenField` for it.
          for unique_constraint_name in unique_constraint_names:
            # Get the model field that is referred too.
              unique_constraint_field = model._meta.get_field(unique_constraint_name)
  
              if getattr(unique_constraint_field, 'auto_now_add', None):
                  default = CreateOnlyDefault(timezone.now)
              elif getattr(unique_constraint_field, 'auto_now', None):
keep keep keep keep replace keep keep keep keep keep
 Removed unused imports, pep8 fixes, typo fixes 
rest_framework/serializers.py