parse a tuple of 3 uint8 values

def uint8_3(self, name):
        """parse a tuple of 3 uint8 values"""
        self._assert_is_string(name)
        frame = self._next_frame()
        if len(frame) != 3:
            raise MessageParserError("Expected exacty 3 byte for 3 unit8 values")
        vals = unpack("BBB", frame)
        self.results.__dict__[name] = vals
        return self