works for -2pi < Ms < 2pi, e <= 0.97

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