  from rest_framework.validators import (
      UniqueForDateValidator, UniqueForMonthValidator, UniqueForYearValidator,
      UniqueTogetherValidator
  )
  import copy
  import inspect
  import warnings
  
  # Note: We do the following so that users of the framework can use this style:
  #
  #     example_field = serializers.CharField(...)
  #
 
</s> remove from django.core.exceptions import ImproperlyConfigured
from django.core.exceptions import ValidationError as DjangoValidationError
 </s> add import warnings
 </s> remove from rest_framework.compat import OrderedDict
from rest_framework.exceptions import ValidationError
from rest_framework.fields import empty, set_value, Field, SkipField
from rest_framework.settings import api_settings
from rest_framework.utils import html, model_meta, representation
 </s> add from rest_framework.utils import model_meta </s> remove `ModelSerializer` class and an equivelent explicit `Serializer` class.
 </s> add `ModelSerializer` class and an equivalent explicit `Serializer` class. </s> remove from django.utils import six
 </s> add  </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
  from rest_framework.validators import (
      UniqueForDateValidator, UniqueForMonthValidator, UniqueForYearValidator,
      UniqueTogetherValidator
  )



  
  # Note: We do the following so that users of the framework can use this style:
  #
  #     example_field = serializers.CharField(...)
  #
keep keep keep keep replace replace replace keep keep keep keep keep
 Removed unused imports, pep8 fixes, typo fixes 
rest_framework/serializers.py