https://github.com/thom311/libnl/blob/libnl3_2_25/lib/handlers.c#L114.

def nl_msg_in_handler_debug(msg, arg):
    """https://github.com/thom311/libnl/blob/libnl3_2_25/lib/handlers.c#L114."""
    ofd = arg or _LOGGER.debug
    ofd('-- Debug: Received Message:')
    nl_msg_dump(msg, ofd)
    return NL_OK