corewise_stack_sum
==================

.. py:function:: t3toolbox.corewise.corewise_stack_sum(X, axis, n_stack)

   .. code-block:: python

      def corewise_stack_sum(
              X:          NDArrayTree,  # tree; each leaf shape = stack_shape + (core dims)
              axis,                     # stack axis/axes (None -> all; negatives wrap rel. to n_stack)
              n_stack:    int,          # number of leading stack axes axis is normalized against
      ) -> NDArrayTree:                 # same tree structure as X, summed stack axes removed


   Sum each leaf over stack axes, vectorized.

   Normalizes ``axis`` against the ``n_stack`` leading (stack) axes (``None`` -> all of them; negative
   axes wrap relative to ``n_stack``), then :py:func:`corewise_sum` over those axes.

   .. rubric:: Examples

   >>> import numpy as np
   >>> import t3toolbox.corewise as cw
   >>> X = (np.ones((2, 3, 4)),)   # stack=(2, 3), then a core axis
   >>> print(cw.corewise_stack_sum(X, None, 2)[0].shape)   # sum both stack axes
   (4,)