Given an array of integers arr, write a function that returns true if and only if the number of occurrences of each value in the array is unique.
Example 1:
Input: arr = [1,2,2,1,1,3]
Output: true
Explanation: The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences.
Example 2:
Input: arr = [1,2]
Output: false
Example 3:
Input: arr = [-3,0,1,-3,1,1,1,-3,10,0]
Output: true
Constraints:
1 <= arr.length <= 1000
-1000 <= arr[i] <= 1000
class Solution:
    def uniqueOccurrences(self, arr: List[int]) -> bool:
        rec = [arr.count(elem) for elem in set(arr)]
        return len(rec) == len(set(rec))

class Solution:
    def uniqueOccurrences(self, arr: List[int]) -> bool:
        rec = [arr.count(elem) for elem in set(arr)]
        return len(rec) == len(set(rec))
