code: def inside_sphere_points(xyz, center, radius):
      r"""If a track intersects with a sphere of a specified center and
      radius return the points that are inside the sphere otherwise False.
      Mathematically this can be simply described by $|x-c| \le r$ where $x$
      a point $c$ the center of the sphere and $r$ the radius of the
      sphere.
  
      Parameters
      ----------
      xyz : array, shape (N,3)
         representing x,y,z of the N points of the track
      center : array, shape (3,)
         center of the sphere
      radius : float
         radius of the sphere
  
      Returns
      -------
      xyzn : array, shape(M,3)
         array representing x,y,z of the M points inside the sphere
  
      Examples
      --------
      >>> from dipy.tracking.metrics import inside_sphere_points
      >>> line=np.array(([0,0,0],[1,1,1],[2,2,2]))
      >>> sph_cent=np.array([1,1,1])
      >>> sph_radius = 1
      >>> inside_sphere_points(line,sph_cent,sph_radius)
      array([[1, 1, 1]])
      """
      return xyz[
          (np.sqrt(np.sum((xyz - center) ** 2, axis=1)) <= radius)
      ]
  
imports: from dipy.utils.deprecator import deprecate_with_version
  from dipy.tracking.streamline import set_number_of_points
  import numpy
  from scipy.interpolate import splprep, splev
label_desc: Use image node_id 15 for calling a global function with example usage: inside_sphere_points(xyz, center, radius) and returns: xyz