  
      def get_url_field(self):
          return None
  
      def get_pk_field(self, model_field):
          """
          Returns a default instance of the pk field.
          """
          return self.get_field(model_field)
  
 
</s> remove         return self.get_field(model_field)
 </s> add         return self.get_field(field_name, model_field) </s> remove     def get_nested_field(self, model_field, related_model, to_many, has_through_model):
 </s> add     def get_nested_field(self, field_name, model_field, related_model, to_many, has_through_model): </s> remove     def get_related_field(self, model_field, related_model, to_many, has_through_model):
 </s> add     def get_related_field(self, field_name, model_field, related_model, to_many, has_through_model): </s> remove     def get_field(self, model_field):
 </s> add     def get_field(self, field_name, model_field): </s> remove     def get_pk_field(self, model_field):
 </s> add     def get_pk_field(self, field_name, model_field):
    def get_pk_field(self, field_name, model_field):
  
      def get_url_field(self):
          return None
  
    def get_pk_field(self, field_name, model_field):
          """
          Returns a default instance of the pk field.
          """
          return self.get_field(model_field)
  
keep keep keep keep replace keep keep keep keep keep
 Drop label from serializer fields when not needed 
rest_framework/serializers.py