      unicode_to_repr,
      DurationField as ModelDurationField,
  )
  from rest_framework.utils import model_meta
  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.validators import (
 
</s> remove from rest_framework.compat import (
    postgres_fields,
    unicode_to_repr,
    DurationField as ModelDurationField,
 </s> add from django.db.models.fields import (
    FieldDoesNotExist, Field as DjangoModelField </s> remove import inspect
 </s> add 
from rest_framework.compat import (
    postgres_fields, unicode_to_repr, DurationField as ModelDurationField,
      unicode_to_repr,
      DurationField as ModelDurationField,
  )
  from rest_framework.utils import model_meta
from rest_framework.compat import (
    postgres_fields, unicode_to_repr, DurationField as ModelDurationField,
from rest_framework.compat import (
    postgres_fields, unicode_to_repr, DurationField as ModelDurationField,
from rest_framework.compat import (
    postgres_fields, unicode_to_repr, DurationField as ModelDurationField,
from rest_framework.compat import (
    postgres_fields, unicode_to_repr, DurationField as ModelDurationField,
  )
  from rest_framework.utils.serializer_helpers import (
      ReturnDict, ReturnList, BoundField, NestedBoundField, BindingDict
  )
  from rest_framework.validators import (
keep keep keep keep replace replace replace replace keep keep keep keep keep
 Cleanup import following PEP 8 style guide 
rest_framework/serializers.py