code: def _solve_cholesky(Q, z):
      L, info = potrf(Q, lower=False, overwrite_a=False, clean=False)
      if info > 0:
          msg = "%d-th leading minor not positive definite" % info
          raise la.LinAlgError(msg)
      if info < 0:
          msg = (
              "illegal value in %d-th argument of internal potrf"
              % -info
          )
          raise ValueError(msg)
      f, info = potrs(L, z, lower=False, overwrite_b=False)
      if info != 0:
          msg = (
              "illegal value in %d-th argument of internal potrs"
              % -info
          )
          raise ValueError(msg)
      return f
  
imports: import warnings
  import numpy
  import numbers
  from scipy.integrate import quad
  from scipy.special import lpn, gamma
  import scipy.linalg
  import scipy.linalg.lapack
  from dipy.data import small_sphere, get_sphere, default_sphere
  from dipy.core.geometry import cart2sphere
  from dipy.core.ndindex import ndindex
  from dipy.sims.voxel import single_tensor
  from dipy.reconst.multi_voxel import multi_voxel_fit
  from dipy.reconst.dti import TensorModel, fractional_anisotropy
  from dipy.reconst.shm import sph_harm_ind_list, real_sh_descoteaux_from_index, sph_harm_lookup, lazy_index, SphHarmFit, real_sh_descoteaux, sh_to_rh, forward_sdeconv_mat, SphHarmModel
  from dipy.reconst.utils import _roi_in_volume, _mask_from_roi
  from dipy.direction.peaks import peaks_from_model
  from dipy.core.geometry import vec2vec_rotmat
  from dipy.utils.deprecator import deprecate_with_version, deprecated_params
label_desc: Use image node_id 5 for calling a global function with example usage: _solve_cholesky(Q, z) and returns: f