fv_variations_from_vector
=========================

.. py:function:: t3toolbox.backend.fv_operations.fv_variations_from_vector(flat, variation_shapes, stack_shape = ())

   .. code-block:: python

      def fv_variations_from_vector(
              flat:               NDArray,            # shape=(size,)
              variation_shapes:   VariationShapes,
              stack_shape:        typ.Sequence[int] = (),
      ) -> Variations:


   Rebuild variation cores from a 1D vector (inverse of flattening the variation cores).

   Each core is reshaped to ``stack_shape + core_shape``, consuming the flat vector in order
   (tucker-variation cores first, then tt-variation cores).