@classmethod
def decode(cls, stream):
    """Decodes generic data sub-item from data stream

        User data value is left in raw string format. The Application Entity
        is responsible for dealing with it.

        :param stream: raw data stream
        :return: decoded generic data sub-item
        """
    item_type, reserved, item_length = cls.header.unpack(stream.read(4))
    user_data = stream.read(int(item_length))
    return cls(item_type=item_type, user_data=user_data, reserved=reserved)
