lenskit.splitting.HoldoutMethod
===============================

.. py:class:: lenskit.splitting.HoldoutMethod
   :canonical: lenskit.splitting._holdout.HoldoutMethod

   Bases: :py:obj:`Protocol`


   Holdout methods select test rows for a user (or occasionally an item).
   Partition methods are callable; when called with a data frame, they return
   the test entries.

   :Stability: Caller


   .. py:method:: __call__(items)
      :abstractmethod:


      Subset an item list (in the uncommon case of item-based holdouts, the
      item list actually holds user IDs).

      :param udf: The item list from which holdout items should be selected.

      :returns: The list of test items.