Hessian, HVP, and IHVP
=======
.. autofunction:: dattri.func.hessian.hvp
.. autofunction:: dattri.func.hessian.hvp_at_x

.. autofunction:: dattri.func.hessian.ihvp_explicit
.. autofunction:: dattri.func.hessian.ihvp_at_x_explicit

.. autofunction:: dattri.func.hessian.ihvp_cg
.. autofunction:: dattri.func.hessian.ihvp_at_x_cg

.. autofunction:: dattri.func.hessian.ihvp_arnoldi
.. autofunction:: dattri.func.hessian.ihvp_at_x_arnoldi

.. autofunction:: dattri.func.hessian.ihvp_lissa
.. autofunction:: dattri.func.hessian.ihvp_at_x_lissa