fv_frame_reverse
================

.. py:function:: t3toolbox.backend.fv_operations.fv_frame_reverse(frame)

   .. code-block:: python

      def fv_frame_reverse(
              frame: typ.Tuple[
                  typ.Sequence[NDArray],  # up_tucker_cores
                  typ.Sequence[NDArray],  # down_tt_cores
                  typ.Sequence[NDArray],  # left_tt_cores
                  typ.Sequence[NDArray],  # right_tt_cores
              ],
      ) -> typ.Tuple[
          typ.Tuple[NDArray, ...],  # up_tucker_cores  (mode order reversed)
          typ.Tuple[NDArray, ...],  # down_tt_cores
          typ.Tuple[NDArray, ...],  # left_tt_cores    (= reversed old right cores)
          typ.Tuple[NDArray, ...],  # right_tt_cores   (= reversed old left cores)
      ]:


   Reverse the mode order of a T3 frame 4-tuple ``(up, down, left, right)``.

   The left and right TT families **swap roles**: reversing a left-orthogonal chain yields a
   right-orthogonal one, so the new left family is the reversed old *right* family and vice versa
   (the up-tucker family is reversed; the down family is reversed per :py:func:`tt_reverse`). The
   redundant left/right store makes this exact with no re-orthogonalization. Inverse of itself.