code: def npa(self, odf, width=5):
      """non-parametric anisotropy
  
      Nimmo-Smith et al.  ISMRM 2011
      """
      # odf = self.odf(s)
      t0, t1, t2 = triple_odf_maxima(self.odf_vertices, odf, width)
      psi0 = t0[1] ** 2
      psi1 = t1[1] ** 2
      psi2 = t2[1] ** 2
      npa = np.sqrt(
          (psi0 - psi1) ** 2 + (psi1 - psi2) ** 2 + (psi2 - psi0) ** 2
      ) / np.sqrt(2 * (psi0**2 + psi1**2 + psi2**2))
      # print 'tom >>>> ',t0,t1,t2,npa
  
      return t0, t1, t2, npa
  
imports: import numpy
  from dipy.reconst.odf import OdfModel, OdfFit
  from dipy.reconst.cache import Cache
  import warnings
  from dipy.reconst.multi_voxel import multi_voxel_fit
label_desc: Use image node_id 3 for calling a global function with example usage: npa(odf, width) and returns: t0,  t1,  t2,  npa