public void set_auto_flush_bus
Usually, when a pipeline goes from READY to NULL state, it automatically flushes all pending messages on the bus, which is done for refcounting
purposes, to break circular references.
This means that applications that update state using (async) bus messages (e.g. do certain things when a pipeline goes from PAUSED to READY)
might not get to see messages when the pipeline is shut down, because they might be flushed before they can be dispatched in the main thread.
This behaviour can be disabled using this function.
It is important that all messages on the bus are handled when the automatic flushing is disabled else memory leaks will be introduced.
||whether or not to automatically flush the bus when the pipeline goes from READY to NULL state