How to use the pybase64.standard_b64encode function in pybase64

def unpack(self, payload, offset, length):
        res, offset, length = self._unpack_members(payload, offset, length)

        res['preamble'] = self.preamble
        res['msg_type'] = self.msg_type
        res['sender'] = self.sender
        if self.payload is not None:
            res['payload'] = standard_b64encode(self.payload.tobytes()).decode('ascii')
        res['crc'] = self.crc
        res['length'] = self.length
        return res, offset, length