code: def _energy_hessian(self):
      return (
          (1 / self._V - 1 / self._V0) * self._H
          - np.dot(self._dV, self._dV.T)
          / np.maximum(self._V**2, SMALL)
          + np.dot(self._dV0, self._dV0.T)
          / np.maximum(self._V0**2, SMALL)
      )
  
imports: import os
  import warnings
  import numpy
  from nibabel import io_orientation
  from nibabel.affines import apply_affine
  from ...core.image.image_spaces import as_xyz_image, make_xyz_image, xyz_affine
  from ...io.nibcompat import get_header
  from ..slicetiming import timefuncs
  from ._registration import _cspline_sample3d, _cspline_sample4d, _cspline_transform
  from .affine import Affine, Rigid
  from .optimizer import configure_optimizer, use_derivatives
  from .type_check import check_type, check_type_and_shape
label_desc: Use image node_id 10 for calling the Realign4dAlgorithm obj's underlying member method code with example usage: obj._energy_hessian() and returns: unknown