Encrypt a string.

        input: unicode str, output: unicode str

def encrypt_text(self, text, *args, **kwargs):
        """
        Encrypt a string.

        input: unicode str, output: unicode str
        """
        b = text.encode("utf-8")
        token = self.encrypt(b, *args, **kwargs)
        return base64.b64encode(token).decode("utf-8")