docs: def unique(self, drop_dups=False):
          ''' Make this index unique, optionally dropping duplicate entries.
  
              :param drop_dups: Drop duplicate objects while creating the unique \
                  index?  Default to ``False``
          '''
          self.__unique = True
          if drop_dups and pymongo.version_tuple >= (2, 7, 5): # pragma: nocover
              raise BadIndexException("drop_dups is not supported on pymongo >= 2.7.5")
          self.__drop_dups = drop_dups
          return self