Implement Queue using Stacks

1class MyQueue:
2    def __init__(self):
3        self.s1 = []
4        self.s2 = []
5
6    def push(self, x: int) -> None:
7        self.s1.append(x)
8
9    def pop(self) -> int:
10        self._move()
11        return self.s2.pop()
12
13    def peek(self) -> int:
14        self._move()
15        return self.s2[-1]
16
17    def empty(self) -> bool:
18        return not self.s1 and not self.s2
19
20    def _move(self) -> None:
21        if not self.s2:
22            while self.s1:
23                self.s2.append(self.s1.pop())