def parent(*args)
      return @parent if args.empty?
      key = args.shift

      @parent = Gretel::Crumb.new(context, key, *args)
    end
def parent(*args)
      return @parent if args.empty?
      key = args.shift

      @parent = Gretel::Crumb.new(context, key, *args)
    end
Sets or gets the parent breadcrumb.
 If you supply a parent key and optional arguments, it will set the parent.
 If nothing is supplied, it will return the parent, if this has been set.

 Example:
   parent :category, category

 Or short, which will infer the key from the model's `model_name`:
   parent category