extends ReadOnlyReactiveCollectionBase class_name ReactiveCollectionBase func reset(): NotImplementedError.raise() func add_item(item) -> int: NotImplementedError.raise() return -1 func remove_item(item) -> int: NotImplementedError.raise() return -1 func remove_at(index : int) -> Variant: NotImplementedError.raise() return null func replace_item(item, with) -> int: NotImplementedError.raise() return -1 func replace_at(index : int, item) -> Variant: NotImplementedError.raise() return null func swap(idx1 : int, idx2 : int) -> Tuple: NotImplementedError.raise() return Tuple.Empty() func move_to(curr_index : int, new_index : int): NotImplementedError.raise() func insert_at(index : int, elem): NotImplementedError.raise()