              raise ValueError("Hyperlinked field requires 'view_name' kwarg")
  
          self.slug_field = kwargs.pop('slug_field', self.slug_field)
          default_slug_kwarg = self.slug_url_kwarg or self.slug_field
          self.pk_url_kwarg = kwargs.pop('pk_url_kwarg', self.pk_url_kwarg)
          self.slug_url_kwarg = kwargs.pop('slug_url_kwarg', default_slug_kwarg)
  
          self.format = kwargs.pop('format', None)
          super(HyperlinkedRelatedField, self).__init__(*args, **kwargs)
  
 
</s> remove         self.format = kwargs.pop('format', None)
 </s> add  </s> remove     def get_slug_field(self):
 </s> add     def get_url(self, obj, view_name, request, format): </s> remove         Get the name of a slug field to be used to look up by slug.
        """
        return self.slug_field

    def to_native(self, obj):
        view_name = self.view_name
        request = self.context.get('request', None)
        format = self.format or self.context.get('format', None)

        if request is None:
            warnings.warn("Using `HyperlinkedRelatedField` without including the "
                          "request in the serializer context is deprecated. "
                          "Add `context={'request': request}` when instantiating the serializer.",
                          DeprecationWarning, stacklevel=4)
 </s> add         Given an object, return the URL that hyperlinks to the object.
              raise ValueError("Hyperlinked field requires 'view_name' kwarg")
  
          self.slug_field = kwargs.pop('slug_field', self.slug_field)
          default_slug_kwarg = self.slug_url_kwarg or self.slug_field

          self.slug_url_kwarg = kwargs.pop('slug_url_kwarg', default_slug_kwarg)
  
          self.format = kwargs.pop('format', None)
          super(HyperlinkedRelatedField, self).__init__(*args, **kwargs)
  
keep keep keep keep replace keep keep keep keep keep
 lookup_field on hyperlinked fields, and overriddable hyperlinked fields.  Closes #688 
rest_framework/relations.py