  )
  from rest_framework.utils.serializer_helpers import (
      ReturnDict, ReturnList, BoundField, NestedBoundField, BindingDict
  )
  from rest_framework.validators import (
      UniqueForDateValidator, UniqueForMonthValidator, UniqueForYearValidator,
      UniqueTogetherValidator
  )
  
 
</s> remove from rest_framework.utils.field_mapping import (
    get_url_kwargs, get_field_kwargs,
    get_relation_kwargs, get_nested_relation_kwargs,
    ClassLookupDict
 </s> add from rest_framework.compat import (
    postgres_fields, unicode_to_repr, DurationField as ModelDurationField, </s> remove import warnings
 </s> add  </s> remove import inspect
 </s> add 
from rest_framework.utils.field_mapping import (
    get_url_kwargs, get_field_kwargs, get_relation_kwargs,
    get_nested_relation_kwargs, ClassLookupDict
)
  )
  from rest_framework.utils.serializer_helpers import (
      ReturnDict, ReturnList, BoundField, NestedBoundField, BindingDict
  )
from rest_framework.utils.field_mapping import (
    get_url_kwargs, get_field_kwargs, get_relation_kwargs,
    get_nested_relation_kwargs, ClassLookupDict
)
  from rest_framework.validators import (
      UniqueForDateValidator, UniqueForMonthValidator, UniqueForYearValidator,
      UniqueTogetherValidator
  )
  
keep keep keep add keep keep keep keep keep
 Cleanup import following PEP 8 style guide 
rest_framework/serializers.py