ut3_entries_derivatives
=======================

.. py:function:: t3toolbox.backend.ut3_sampling.ut3_entries_derivatives(index, pp, data, order)

   .. code-block:: python

      def ut3_entries_derivatives(
              index: NDArray,                # int, shape=(d,)+W -- the grid points
              pp:    typ.Sequence[NDArray],  # perturbation vectors P, len=d, ith elm_shape=W+(Ni,)
              data:  UT3Data,
              order: int,                    # highest derivative order
      ) -> NDArray:                          # shape=(order+1,)+W+stack_shape


   Symmetric entry derivatives of a uniform Tucker tensor train at ``index`` (shares
   ``sampling_derivatives.t3_entries_derivatives``; the up-index jet slices Tucker fibers, so only ``pp`` is
   packed -- ``index`` in ``[0,Ni)`` hits the real prefix).