Design a HashSet without using any built-in hash table libraries.

Implement `MyHashSet` class:

- `void add(key)` Inserts the value `key` into the HashSet.
- `bool contains(key)` Returns whether the value `key` exists in the HashSet or not.
- `void remove(key)` Removes the value `key` in the HashSet. If `key` does not exist in the HashSet, do nothing.

Example 1:

    Input
    ["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
    [[], [1], [2], [1], [3], [2], [2], [2], [2]]
    Output
    [null, null, null, true, false, null, true, null, false]

    Explanation
    MyHashSet myHashSet = new MyHashSet();
    myHashSet.add(1);      // set = [1]
    myHashSet.add(2);      // set = [1, 2]
    myHashSet.contains(1); // return True
    myHashSet.contains(3); // return False, (not found)
    myHashSet.add(2);      // set = [1, 2]
    myHashSet.contains(2); // return True
    myHashSet.remove(2);   // set = [1]
    myHashSet.contains(2); // return False, (already removed)

Constraints:

- `0 <= key <= 106`
- At most `104` calls will be made to `add`, `remove`, and `contains`.