def METHOD_NAME(channels, channel_id):
    """
    Get the id of the live video broadcasted by the channel
    None if channel cannot be found or it hasn't any video / live info associated.
    """
    for channel in channels:
        if channel.get('id') == channel_id:
            if channel.get('items', None) is not None:
                for item in channel.get('items', []):
                    live_id = item.get('video_id', None)
                    if live_id is not None:
                        return live_id
    return None