code: def _slice_one_sample(ptarget, x0, w, rs):
      """Slice sampling for one sample
  
      Parameters
      ----------
      ptarget : function with one input
          The target pdf to sample from or a multiple of it.
      x0 : array
          Initial state for the MCMC procedure. Note that the shape of this array
          defines the dimensionality n_dim of the data points to be sampled.
      w : float
          Initial bracket width.
      rs : int, RandomState instance or None
          Pass an int for reproducible output across multiple function calls.
  
      Returns
      -------
      sample : ndarray, shape (n_dim,)
          Sample from the target pdf.
      """
      xt = np.copy(x0)
      n_dim = len(x0)
  
      for i in range(n_dim):
          ei = np.zeros(n_dim)
          ei[i] = 1
  
          # step 1 : evaluate ptarget(xt)
          Px = ptarget(xt)
  
          # step 2 : draw vertical coordinate uprime ~ U(0, ptarget(xt))
          uprime_i = Px * rs.rand()
  
          # step 3 : create a horizontal interval (xl_i, xr_i) enclosing xt_i
          r = rs.rand()
          xl_i = xt[i] - r * w
          xr_i = xt[i] + (1 - r) * w
          while ptarget(xt + (xl_i - xt[i]) * ei) > uprime_i:
              xl_i = xl_i - w
          while ptarget(xt + (xr_i - xt[i]) * ei) > uprime_i:
              xr_i = xr_i + w
  
          # step 4 : loop
          while True:
              xprime_i = xl_i + (xr_i - xl_i) * rs.rand()
              Px = ptarget(xt + (xprime_i - xt[i]) * ei)
              if Px > uprime_i:
                  break
              else:
                  if xprime_i > xt[i]:
                      xr_i = xprime_i
                  else:
                      xl_i = xprime_i
  
          # store coordinate i of new sample
          xt = np.copy(xt)
          xt[i] = xprime_i
  
      return xt
  
file_path: pyRiemann/pyriemann/datasets/sampling.py
imports: from functools import partial
  import warnings
  import numpy
  from scipy.stats import multivariate_normal
  from sklearn.utils import check_random_state
  from joblib import Parallel, delayed
  from ..utils.base import sqrtm, expm
  from ..utils.test import is_sym_pos_semi_def
label_desc: Use image node_id 5 for calling a global function with example usage: _slice_one_sample(ptarget, x0, w, rs) and returns: xt