ut3_leaf_structure
==================

.. py:function:: t3toolbox.backend.ut3_operations.ut3_leaf_structure(d)

   .. code-block:: python

      def ut3_leaf_structure(d: int):  # leaf-structure template for stacking.apply_func_to_leaf_subtrees


   Template marking one uniform-T3 ``.data`` leaf for the tree machinery in ``stacking.py``.

   The leaf is ``(tucker_supercore, tt_supercore, shape, (tucker_mask, tt_mask))``. The ``shape``
   int tuple has ``d`` int leaves, so the template must encode its length: a bare ``None`` there
   fails to match (an int tuple is a ``Sequence``, unlike the ndarray leaves, so the walker would
   recurse into it).