'The Newton point is a global minimum of the approximate function.'

def newton_point(self):

    if (self._newton_point is None):
        g = self.jac
        B = self.hess
        cho_info = scipy.linalg.cho_factor(B)
        self._newton_point = (- scipy.linalg.cho_solve(cho_info, g))
    return self._newton_point
