@staticmethod
def _get_data_format_3(raw):
    """
        Validate that data is from RuuviTag and is Data Format 3

        Returns:
            string: Sensor data
        """
    try:
        if 'FF990403' not in raw:
            return None
        payload_start = raw.index('FF990403') + 6
        return raw[payload_start:]
    except:
        return None
