При использовании модуля ffmpeg-python как правильно вести аргумент в фильтр?

Question

[Валентин]

При вводе

try:
    stream = ffmpeg.input(f'{source_path}\{g}\{filename}')
    stream = ffmpeg.filter_(stream, "pan", 'mono|c0=c0|')
    #stream = ffmpeg.filter_(stream,"lowpass", '500')
    stream = ffmpeg.output(stream, f'{source_path}\{g}\{filename}_remfreq.wav')
    ffmpeg.run(stream, capture_stdout=True, capture_stderr=True)
except FFmpegError as e:
    print('stdout:', e.stdout.decode('utf8'))
    print('stderr:', e.stderr.decode('utf8'))
    raise e

получаю

[Parsed_pan_0 @ 0000026ebc1ace40] Syntax error after channel name in "c0\=c0"
[AVFilterGraph @ 0000026ebc1cfa00] Error initializing filter 'pan' with args 'mono|c0\\\=c0|'
Error initializing complex filters.
Invalid argument

Как сделать чтоб передавалось не 'mono|c0\\\=c0|' а 'mono|c0=c0|' ?