Design HashSet Python Solution with Tests

lcpy gen -n 705   # by problem number
lcpy gen -s design_hash_set   # by problem name

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)

class MyHashSet:
    # Time: O(1)
    # Space: O(n)
    def __init__(self) -> None:
        # Problem guarantees 0 <= key <= 10^6; a direct-address table is simplest.
        self._present: list[bool] = [False] * 1_000_001

    # Time: O(1)
    # Space: O(1)
    def add(self, key: int) -> None:
        self._present[key] = True

    # Time: O(1)
    # Space: O(1)
    def remove(self, key: int) -> None:
        self._present[key] = False

    # Time: O(1)
    # Space: O(1)
    def contains(self, key: int) -> bool:
        return self._present[key]