          field_class = self.serializer_related_field
          field_kwargs = get_relation_kwargs(field_name, relation_info)
  
          # `view_name` is only valid for hyperlinked relationships.
          if not issubclass(field_class, HyperlinkedRelatedField):
              field_kwargs.pop('view_name', None)
  
          return field_class, field_kwargs
  
 
</s> remove     model_field, related_model, to_many, has_through_model = relation_info
 </s> add     model_field, related_model, to_many, to_field, has_through_model = relation_info
        to_field = field_kwargs.pop('to_field', None)
        if to_field and to_field != 'id':
            field_kwargs['slug_field'] = to_field
            field_class = self.serializer_related_to_field

          field_class = self.serializer_related_field
          field_kwargs = get_relation_kwargs(field_name, relation_info)
  
        to_field = field_kwargs.pop('to_field', None)
        if to_field and to_field != 'id':
            field_kwargs['slug_field'] = to_field
            field_class = self.serializer_related_to_field

          # `view_name` is only valid for hyperlinked relationships.
          if not issubclass(field_class, HyperlinkedRelatedField):
              field_kwargs.pop('view_name', None)
  
          return field_class, field_kwargs
  
keep keep add keep keep keep keep keep keep
 Added support for the to_field on ForeignKey fields 
rest_framework/serializers.py