def _second(self):
        """Find Smith normal form for Right-low 2x2 matrix"""

        self._second_one_loop()
        A = self._A
        if A[2, 1] == 0:
            return True
        elif A[2, 1] % A[1, 1] == 0:
            self._second_finalize()
            self._Ps += self._L
            self._L = []
            return True
        else:
            return False
Find Smith normal form for Right-low 2x2 matrix