python-leetcode - 342. Power of Four

342. Power of Four
     Easy

Given an integer n, return true if it is a power of four. Otherwise, return false.

An integer n is a power of four, if there exists an integer x such that n == 4x.

Example 1:

Input: n = 16
Output: true
Example 2:

Input: n = 5
Output: false
Example 3:

Input: n = 1
Output: true

Constraints:

-231 <= n <= 231 - 1

class Solution:
    def isPowerOfFour(self, n: int) -<