code: def _set_backreferences(self, context, items, **kwargs):
          
  
          # Don't set any references during initialization.
          # This might cause a recursion error when calling `getRaw` to fetch the
          # current set UIDs!
          initializing = kwargs.get('_initializing_', False)
          if initializing:
              return
  
          # UID of the current object
          uid = api.get_uid(context)
          # current set UIDs
          raw = self.getRaw(context) or []
          # handle single reference fields
          if isinstance(raw, basestring):
              raw = [raw, ]
          cur = set(raw)
          # UIDs to be set
          new = set(map(api.get_uid, items))
          # removed UIDs
          removed = cur.difference(new)
  
          # Unlink removed UIDs from the source
          for uid in removed:
              source = api.get_object_by_uid(uid, None)
              if source is None:
                  logger.warn("UID {} does not exist anymore".format(uid))
                  continue
              self.unlink_reference(source, context)
  
          # Link backrefs
          for item in items:
              self.link_reference(item, context)
docs: Set the back references on the linked items
  
          This will set an annotation storage on the referenced items which point
          to the current context.