docs: def Efn(Ms,eccs):
      """works for -2pi < Ms < 2pi, e <= 0.97"""
      Ms = np.atleast_1d(Ms)
      eccs = np.atleast_1d(eccs)
      unit = np.floor(Ms / (2*np.pi))
      Es = EFN((Ms % (2*np.pi)),eccs)
      Es += unit*(2*np.pi)
      return Es