docstr: Compute streamlines mean-points
docstr_tok: ["Compute","streamlines","mean-points"]
code: def _slines_mean_points(self, slines_arr):
      """Compute streamlines mean-points"""
      r_arr = slines_arr.reshape((len(slines_arr), self.nb_mpts, -1, 3))
      mpts = np.mean(r_arr, axis=2)
      return mpts.reshape(len(slines_arr), -1)
  
file_path: dipy/dipy/segment/fss.py
imports: import warnings
  import numpy
  from scipy.sparse import coo_matrix
  from scipy.spatial import cKDTree
  from dipy.tracking.streamline import set_number_of_points
  from dipy.segment.metric import mean_euclidean_distance
  from dipy.io.stateful_tractogram import StatefulTractogram
label_desc: Use image node_id 5 for calling the FastStreamlineSearch obj's underlying member method code with example usage: obj._slines_mean_points(slines_arr) and returns: mpts