async def METHOD_NAME(self, ctx, bg_type: str, user_id: str, img_url: str):
    """Set one-time custom background
    bg_type can be: `profile`, `rank` or `levelup`."""
    valid_types = ["profile", "rank", "levelup"]
    type_input = bg_type.lower()
    if type_input not in valid_types:
        await ctx.send("Please choose a valid type. Must be `profile`, `rank` or `levelup`.")
        return
    # test if valid user_id
    userinfo = await self.db.users.find_one({"user_id": str(user_id)})
    if not userinfo:
        await ctx.send("That is not a valid user id!")
        return
    if not await self._valid_image_url(img_url):
        await ctx.send("That is not a valid image URL!")
        return
    await self.db.users.update_one(
        {"user_id": str(user_id)},
        {"$set": {"{}_background".format(type_input): img_url}},
    )
    await ctx.send("User {} custom {} background set.".format(user_id, bg_type))