t3_corewise_frame
=================

.. py:function:: t3toolbox.backend.fv_conversions.t3_corewise_frame(x_cores)

   .. code-block:: python

      def t3_corewise_frame(
              x_cores:  typ.Tuple,   # (tucker_cores, tt_cores)
      ) -> typ.Tuple:                # (U, O, P, Q) = (U, G, G, G); the raw cores ARE the frame


   The **corewise** frame of a T3: the Section 6.3 substitution ``(P, Q, O) -> G``.

   The counterpart of :py:func:`t3_orthogonal_representations` -- the two ways to make a frame from a
   point. Where the orthogonal representation builds an orthonormal frame with a gauge, this one just
   re-labels the cores, which is what makes the corewise geometry the over-parametrized Euclidean one
   (no gauge, additive retraction). Trivial to write and easy to write in the wrong slot order, so it
   is named here rather than open-coded.