Implement a Snapshot Set Iterator

Implement a data structure `SnapshotSet<T>` with the following interface: ```java interface SnapshotSet<T> { void add(T e); void remove(T e); boolean contains(T e); Iterator<T> iterator(); } ``` Requirements: - `add(e)`: adds `e` to the set. - `remove(e)`: removes `e` from the set. - `contains(e)`: returns whether `e` is currently in the set. - `iterator()`: returns an iterator over a **snapshot** of the set at the moment `iterator()` is called. Important behavior: - The returned iterator must continue to iterate over the elements that existed when it was created, even if the set is later modified. - The snapshot is taken when `iterator()` is called, not when iteration begins. - Iteration order does not matter. - Because this is a set, duplicate adds should not create duplicate elements. - Removing a non-existent element can be treated as a no-op. Example: 1. `add(5)`, `add(2)`, `add(8)` 2. `remove(5)` 3. `it = iterator()` → snapshot should represent `{2, 8}` 4. `add(1)` 5. `contains(2)` returns `true` 6. `remove(2)` 7. `contains(2)` returns `false` 8. `add(2)` 9. `it2 = iterator()` → snapshot should represent `{1, 2, 8}` 10. Iterating `it` should still return `{2, 8}` in any order, for example `[2, 8]` Design and implement this data structure.