code: def get_indexer_for(self, target, **kwargs):
          
          if self.is_unique:
              return self.get_indexer(target, **kwargs)
          indexer, _ = self.get_indexer_non_unique(target, **kwargs)
          return indexer
docs: Guaranteed return of an indexer even when non-unique.
  
          This dispatches to get_indexer or get_indexer_nonunique
          as appropriate.