  from django.db.models.constants import LOOKUP_SEP
  from django.db.models.deletion import CASCADE, SET_DEFAULT, SET_NULL
  from django.db.models.query_utils import PathInfo
  from django.db.models.utils import make_model_tuple
  from django.utils import six
  from django.utils.encoding import force_text
  from django.utils.functional import cached_property, curry
  from django.utils.lru_cache import lru_cache
  from django.utils.translation import ugettext_lazy as _
  
 
</s> remove from django.utils import six
 </s> add  </s> remove from django.utils import six
 </s> add  </s> remove from django.utils import six
 </s> add  </s> remove from django.utils import six
 </s> add  </s> remove from django.utils import six
 </s> add 
  from django.db.models.constants import LOOKUP_SEP
  from django.db.models.deletion import CASCADE, SET_DEFAULT, SET_NULL
  from django.db.models.query_utils import PathInfo
  from django.db.models.utils import make_model_tuple

  from django.utils.encoding import force_text
  from django.utils.functional import cached_property, curry
  from django.utils.lru_cache import lru_cache
  from django.utils.translation import ugettext_lazy as _
  
keep keep keep keep replace keep keep keep keep keep
 Refs #23919 -- Removed six.<various>_types usage

Thanks Tim Graham and Simon Charette for the reviews. 
django/db/models/fields/related.py