utv_stack_tangent_stack
=======================

.. py:function:: t3toolbox.backend.utv_operations.utv_stack_tangent_stack(variations_tree)

   .. code-block:: python

      def utv_stack_tangent_stack(
              variations_tree,  # array-like tree (shape K) of variations .data tuples (each stack = C)
      ):  # -> variations .data tuple (stack = K + C)


   Stack a ``K``-shaped tree of variation-``.data`` over the tangent stack ``K`` (outermost; ``C`` stays
   inner). Inverse of :py:func:`utv_unstack_tangent_stack`. The leaves share one frame, so ranks are uniform
   across ``K`` (the masks, constant along ``K``, just replicate).