class_docstr: Points on the unit sphere.
  
  The sphere can be constructed using one of three conventions::
  
    Sphere(x, y, z)
    Sphere(xyz=xyz)
    Sphere(theta=theta, phi=phi)
  
  Parameters
  ----------
  x, y, z : 1-D array_like
      Vertices as x-y-z coordinates.
  theta, phi : 1-D array_like
      Vertices as spherical coordinates.  Theta and phi are the inclination
      and azimuth angles respectively.
  xyz : (N, 3) ndarray
      Vertices as x-y-z coordinates.
  faces : (N, 3) ndarray
      Indices into vertices that form triangular faces.  If unspecified,
      the faces are computed using a Delaunay triangulation.
  edges : (N, 2) ndarray
      Edges between vertices.  If unspecified, the edges are
      derived from the faces.
code: def y(self):
      return self.vertices[:, 1]
  
imports: import numpy
  import warnings
  from scipy import optimize
  from dipy.core.geometry import cart2sphere, sphere2cart, vector_norm
  from dipy.core.onetime import auto_attr
  from dipy.reconst.recspeed import remove_similar_vertices
label_desc: Use image node_id 4 for calling the Sphere obj's underlying member method code with example usage: obj.y() and returns: self