tv_entries
==========

.. py:function:: t3toolbox.backend.entries.tv_entries(index, variation, frame)

   .. code-block:: python

      def tv_entries(
              index:      NDArray,                # int, shape=(d,)+W (index stack W)
              variation:  typ.Tuple[typ.Sequence[NDArray], typ.Sequence[NDArray]],  # (var_tucker, var_tt)
              frame:       typ.Tuple[typ.Sequence[NDArray], typ.Sequence[NDArray],
                                    typ.Sequence[NDArray], typ.Sequence[NDArray]],   # (up, down, left, right)
      ) -> NDArray:                               # entries of the dense tangent at ``index``; shape = W + K + C


   Extract entries of the dense tangent at ``index`` (= apply with unit vectors, by slicing).

   Identical to :py:func:`tv_apply` except the up-index edge variables come from slicing the
   Tucker-core fibers (``U_i[..., index_i]`` and ``dU_i[..., index_i]``) rather than contracting with
   vectors -- so there is no contraction with unit basis vectors and no ``N`` factor.

   .. seealso:: :py:obj:`tv_apply`