init python:
    class SwitchShopCategory(Action):
        def __init__(self, category: str, items: list):
            self.category = category
            self.items = items

        def __call__(self):
            cs = renpy.current_screen()

            if cs is None:
                raise Exception("No current screen.")

            items = self.items
            scope = cs.scope

            scope["shop_items"] = items
            scope["selected_category"] = self.category
            scope["selected_item"] = items[0] if items else None

            renpy.restart_interaction()

    class SortFilter(Action):
        def __init__(self, screenvar: str, sort_keys=None, filter_keys=None):
            self.screenvar = screenvar
            self.filter_keys = filter_keys
            self.sort_keys = sort_keys

        def __call__(self):
            cs = renpy.current_screen()

            if cs is None:
                raise Exception("No current screen.")

            scope = cs.scope
            var = self.screenvar

            if var not in scope:
                raise Exception("Screen var is missing.")

            items = scope[var]

            if self.filter_keys:
                items = self.filter(items, self.filter_keys)
            if self.sort_keys:
                items = self.sort(items, self.sort_keys)

            scope[var] = items
            renpy.restart_interaction()

        @staticmethod
        def filter(items, keys):
            for key in keys:
                if key.startswith("not "):
                    attr = key[4:]
                    items = filter(lambda x: not getattr(x, attr), items)
                else:
                    items = filter(lambda x: getattr(x, key), items)
            return items

        @staticmethod
        def sort(items, keys):
            for key in keys:
                items = sorted(items, key=lambda x: SortFilter.natsort(getattr(x, key)))
            return items

        @staticmethod
        def natsort(s, pattern=re.compile("([0-9]+)")):
            return [int(t) if t.isdigit() else t.lower() for t in pattern.split(str(s))]