async def combine_channel_ids(ctx):
    """Combines all channel IDs.

    Called by `channel_setter` and `channel_deleter`.

    Args:
        ctx (discord.ext.commands.Context): context of the message

    Returns:
        list of int: of Discord channel IDs

    """
    channels = []
    if not ctx.message.channel_mentions:
        channels.append(ctx.channel.id)
    else:
        for channel_mention in ctx.message.channel_mentions:
            channels.append(str(channel_mention.id))
    return channels