title: unhashable type: 'ReturnDict' drf django
body: <p>I'm trying to add but getting this error:</p>
  
  <pre><code>unhashable type: 'ReturnDict'
  </code></pre>
  
  <p>models.py:</p>
  
  <pre><code>class SumInsuredEntity(UUIDBase):
        field_name = CICharField(max_length=255,null=False,blank=False,verbose_name=_("Field Name"), unique=True)
        is_balance = models.ForeignKey(ValidChoice, to_field="key", db_column="is_balance", related_name="is_balance", null=True, blank=True, verbose_name=_("Is Balance"),default='no', on_delete=models.DO_NOTHING) 
        is_thresold = models.ForeignKey(ValidChoice, to_field="key", db_column="is_thresold", related_name="is_thresold", null=True, blank=True, verbose_name=_("Is Thresold"),default='no', on_delete=models.DO_NOTHING)
        status = models.SmallIntegerField(_("Status:1 for Active; 0:InActive"), default=1)
       class Meta:
            db_table = "tpa_master_sieav"
  
       def __str__(self):
          return str(self.uid)
  </code></pre>
  
  <p>Views.py:</p>
  
  <pre><code>@api_view(['POST'])
  def sumInsuredEntityAdd(request):
  '''
  sumInsuredEntity Create Api
  '''
  data= decode_data(request.data.copy())
  serializer_obj = SumInsuredEntitySerializer(data=data)
  if serializer_obj.is_valid(raise_exception=True):
      try:
          sumInsured_save = serializer_obj.save()
          return CustomeResponse(request=request, comment=SUM_INSURED_ENTITY_ADDED_SUCCESSFULLY,data=json.dumps({serializer_obj.data}, cls=UUIDEncoder), message= SUM_INSURED_ENTITY_ADDED_SUCCESSFULLY, status=status.HTTP_200_OK)
      except Exception as e:
          print(e)
          return CustomeResponse(request=request, log_data=json.dumps(str(e), cls=UUIDEncoder), comment=COULD_NOT_SAVE_SUM_INSURED_ENTITY, message=COULD_NOT_SAVE_SUM_INSURED_ENTITY, data=json.dumps({}, cls=UUIDEncoder), status=status.HTTP_400_BAD_REQUEST, validate_errors=1)
  else:
      return CustomeResponse(request=request, comment=FIELDS_NOT_VALID, message=FIELDS_NOT_VALID, data=json.dumps({}, cls=UUIDEncoder), status=status.HTTP_400_BAD_REQUEST, validate_errors=1)
  </code></pre>
  
  <p>its working good but showing error when trying to dump serializer_obj.data</p>