apply_derivatives_kind
======================

.. py:function:: t3toolbox.backend.fitting.apply_derivatives_kind(order, weight = None)

   .. code-block:: python

      def apply_derivatives_kind(
              order:  int,                                # highest derivative order
              weight: typ.Optional[typ.Any] = None,       # ORDER-only residual weight ω, (order+1,); None = 1
      ) -> SamplingKind:                                  # sample = (ww, pp); data = (order+1)+W


   The **apply-derivatives** sampling kind (operator only): symmetric directional derivatives of the
   all-modes apply, orders ``0..order``, in direction ``P``. ``sample = (ww, pp)``. All-modes apply has no
   mode axis, so ``weight`` is **order-only** (a per-mode weight raises -- mode weighting is probe-only).