              return self.get_field(model_field)
  
      def get_url_field(self):
          kwargs = {
              'view_name': self.get_default_view_name(self.opts.model)
          }
          if self.opts.lookup_field:
              kwargs['lookup_field'] = self.opts.lookup_field
          return HyperlinkedIdentityField(**kwargs)
  
 
</s> remove     def get_default_fields(self):
        fields = super(HyperlinkedModelSerializer, self).get_default_fields()

        if self.opts.view_name is None:
            self.opts.view_name = self.get_default_view_name(self.opts.model)

        url_field_name = api_settings.URL_FIELD_NAME
        if url_field_name not in fields:
            ret = fields.__class__()
            ret[url_field_name] = self.get_url_field()
            ret.update(fields)
            fields = ret

        return fields

    def get_pk_field(self, model_field):
        if self.opts.fields and model_field.name in self.opts.fields:
            return self.get_field(model_field)

 </s> add 
            'view_name': view_name
              return self.get_field(model_field)
  
      def get_url_field(self):
          kwargs = {
            'view_name': view_name
          }
          if self.opts.lookup_field:
              kwargs['lookup_field'] = self.opts.lookup_field
          return HyperlinkedIdentityField(**kwargs)
  
keep keep keep keep replace keep keep keep keep keep
 Added help_text argument to fields 
rest_framework/serializers.py