  from django.test import TestCase
  from rest_framework import serializers
  from rest_framework.tests.models import (HasPositiveIntegerAsChoice, Album, ActionItem, Anchor, BasicModel,
      BlankFieldModel, BlogPost, BlogPostComment, Book, CallableDefaultValueModel, DefaultValueModel,
      ManyToManyModel, Person, ReadOnlyManyToManyModel, Photo)
  import datetime
  import pickle
  
  
  class SubComment(object):
 
</s> remove         self.assertEqual(s.errors,  {'decimal_field': ['Ensure that there are no more than 4 digits in total.']}) </s> add 
    ManyToManyModel, Person, ReadOnlyManyToManyModel, Photo, SeveralChoicesModel)
  from django.test import TestCase
  from rest_framework import serializers
  from rest_framework.tests.models import (HasPositiveIntegerAsChoice, Album, ActionItem, Anchor, BasicModel,
      BlankFieldModel, BlogPost, BlogPostComment, Book, CallableDefaultValueModel, DefaultValueModel,
    ManyToManyModel, Person, ReadOnlyManyToManyModel, Photo, SeveralChoicesModel)
  import datetime
  import pickle
  
  
  class SubComment(object):
keep keep keep keep replace keep keep keep keep keep
 Adding `BLANK_CHOICE_DASH` as a choice if the model's field isn't required 
rest_framework/tests/serializer.py