message types to take into account
the next gstreamer.Message matching type that is on the bus, or NULL if the bus is empty or there is no message matching type. The message is taken from the bus and needs to be unreffed with Message.unref after usage.
MT safe.
Get a message matching type from the bus. Will discard all messages on the bus that do not match type and that have been posted before the first message that does match type. If there is no message matching type on the bus, all messages will be discarded. It is not possible to use message enums beyond GST_MESSAGE_EXTENDED in the events mask.