def fdiff(self, argindex=1):
        if len(self.args) == 2:
            z, m = self.args
            if argindex == 1:
                return sqrt(1 - m*sin(z)**2)
            elif argindex == 2:
                return (elliptic_e(z, m) - elliptic_f(z, m))/(2*m)
        else:
            z = self.args[0]
            if argindex == 1:
                return (2*z)/(elliptic_e(z) - elliptic_k(z))
        raise ArgumentIndexError(self, argindex)
dataset/ETHPy150Open sympy/sympy/sympy/functions/special/elliptic_integrals.py/elliptic_e.fdiff/swapped operands of `/`