UT3Variations.sum_stack
=======================

.. py:method:: t3toolbox.uniform_frame_variations_format.UT3Variations.sum_stack(axis=None)

   .. code-block:: python

      def sum_stack(self, axis=None) -> 'UT3Variations':


   Corewise sum over stack axes (a batch of variations -> their sum; the tangent sum, by linearity).
   ``axis`` indexes the stack (default: the whole stack). The mask ORs over the summed axes -- a no-op
   for a same-mask (single-frame) stack; see ``docs/uniform_masks_vs_ranks.md``.