UniformCorewiseGeometry.frame
=============================

.. py:method:: t3toolbox.uniform_manifold.UniformCorewiseGeometry.frame(x)

   .. code-block:: python

      def frame(
              self,
              x:  ut3.UniformTuckerTensorTrain,
      ) -> ubv.UT3Frame:  # the (U, G, G, G) non-orthonormal frame at x


   The core-parameter frame at ``x``: ``(U, G, G, G)`` (down/left/right all the TT supercore ``G``).

   The mask analog of the cores: ``up = down = tucker_edge_mask`` (the U-G Tucker edges) and
   ``left = right = tt_edge_mask`` (the G-G TT bonds, full length ``d+1``) -- the Section 6.3
   substitution ``(P, Q, O) -> G`` gives all three non-up slots the single core ``G``'s rank structure,
   with no boundary slicing (the ``[:-1]`` / ``[1:]`` gauge shift is a *variations*, not a frame,
   thing).