gst-python: Can't set channel positions with GstAudio.AudioInfo.set_format

Submitted by Vladislav Glinsky

Description

Hello, I'm trying to rewrite basic tutorial #8 (https://gstreamer.freedesktop.org/documentation/tutorials/basic/short-cutting-the-pipeline.html) in Python and in original C code we have lines:

GstAudioInfo info;
gst_audio_info_set_format(&info, GST_AUDIO_FORMAT_S16, SAMPLE_RATE, 1, NULL);

I've rewritten them as:

info = GstAudio.AudioInfo()
info.set_format(
format=GstAudio.AudioFormat.S16,
rate=SAMPLE_RATE,
channels=1,
position=None
)

According to documentation and source code of gst_audio_info_set_format last parameter position is nullable (for 1 and 2 channel setup).
Python documents type of position argument as GstAudio.AudioChannelPosition and nothing said if it accepts None, so with Python code above I will get an error: "Argument 4 does not allow None as a value".

I can't pass list of GstAudio.AudioChannelPosition instead - I will get "Expected a GstAudio.AudioChannelPosition, but got list". Isn't list of GstAudio.AudioChannelPosition an equivalent of GstAudioChannelPosition*?

Also it's weird why position in C code is annotated with fixed size of 64 when in fact 64 is the maximum size of channel positions array and channel count argument used to determine actual array size.

Version: 1.12.4