t3_stack
========

.. py:function:: t3toolbox.backend.t3_operations.t3_stack(xx)

   .. code-block:: python

      def t3_stack(
              xx,  # array-like structure of nested tuples containing Tucker tensor trains (stack tree)
      ) -> typ.Tuple[
          typ.Tuple[NDArray, ...],  # stacked_tucker_cores. elm_shape=stack_shape+(ni,Ni)
          typ.Tuple[NDArray, ...],  # stacked_tt_cores.     elm_shape=stack_shape+(rLi,ni,rR(i+1))
      ]: