Implement basic pagination for a list

You are given: - A zero-indexed array of items `items` (you can assume it fits in memory). - An integer `pageSize > 0`. Design and implement a pagination helper that supports the following operations: 1. Initialize the paginator with the array and `pageSize`. 2. Given a **page number** `pageIndex` (0-based), return the subarray of items that belongs to that page. - Page 0 contains items with indices `[0, pageSize - 1]` (if they exist), - Page 1 contains `[pageSize, 2 * pageSize - 1]`, and so on. 3. If `pageIndex` is out of range (no items on that page), return an empty list. Assume: - `0 <= pageIndex` - `1 <= pageSize <= 10^5` - `0 <= len(items) <= 10^6` Define the interface and implement the core method(s) for pagination. Focus on clean indexing and handling boundary cases correctly.