T3Variations.sum_stack
======================

.. py:method:: t3toolbox.frame_variations_format.T3Variations.sum_stack(axis=None)

   .. code-block:: python

      def sum_stack(self, axis=None) -> 'T3Variations':


   Corewise sum over stack axes (a batch of variations -> their sum). ``axis`` indexes the stack
   (default: the whole stack). For variations the corewise sum *is* the tangent sum, by linearity.