  from django.utils import six, timezone
  from django.utils.functional import cached_property
  from django.utils.translation import ugettext_lazy as _
  
  from rest_framework.compat import postgres_fields, unicode_to_repr
  from rest_framework.exceptions import ErrorDetail, ValidationError
  from rest_framework.fields import get_error_detail, set_value
  from rest_framework.settings import api_settings
  from rest_framework.utils import html, model_meta, representation
  from rest_framework.utils.field_mapping import (
 
</s> remove from collections import Mapping, OrderedDict
 </s> add from collections import OrderedDict
from rest_framework.compat import Mapping, postgres_fields, unicode_to_repr
  from django.utils import six, timezone
  from django.utils.functional import cached_property
  from django.utils.translation import ugettext_lazy as _
  
from rest_framework.compat import Mapping, postgres_fields, unicode_to_repr
  from rest_framework.exceptions import ErrorDetail, ValidationError
  from rest_framework.fields import get_error_detail, set_value
  from rest_framework.settings import api_settings
  from rest_framework.utils import html, model_meta, representation
  from rest_framework.utils.field_mapping import (
keep keep keep keep replace keep keep keep keep keep
 Fix Python 3.8 compatibility (#6154) 
rest_framework/serializers.py