Unique occurrence times of leetcode simple questions

subject

Give you an array of integers arr, Please help count the number of occurrences of each number in the array .
If the number of occurrences of each number is unique , Just go back to true; Otherwise return to false.
Example 1：
Input ：arr = [1,2,2,1,1,3]
Output ：true
explain ： In this array ,1 There is 3 Time ,2 There is 2 Time ,3 Only appeared. 1 Time . No two numbers appear the same number .
Example 2：
Input ：arr = [1,2]
Output ：false
Example 3：
Input ：arr = [-3,0,1,-3,1,1,1,-3,10,0]
Output ：true
Tips ：
1 <= arr.length <= 1000
-1000 <= arr[i] <= 1000
source ： Power button （LeetCode）

Their thinking

   First, count the frequency of elements , Then the frequency is de duplicated , If there is no change after weight removal , Then the number of occurrences is unique .

class Solution:
    def uniqueOccurrences(self, arr: List[int]) -> bool:
        return len(set(Counter(arr).values()))==len(Counter(arr))