Decrypt a string.

        input: unicode str, output: unicode str

def decrypt_text(self, text, *args, **kwargs):
        """
        Decrypt a string.

        input: unicode str, output: unicode str
        """
        b = text.encode("utf-8")
        token = base64.b64decode(b)
        return self.decrypt(token, *args, **kwargs).decode("utf-8")