input: Write a python function to find the occurrences of each number in an array using Counter from collections.
  assert findOccurrences([1, 2, 3, 4, 4, 2, 3, 2, 1, 3, 4, 2, 1]) == {1: 3, 2: 4, 3: 3, 4: 3}
  assert findOccurrences([5, 5, 5, 6, 6]) == {5: 3, 6: 2}
  assert findOccurrences([7, 8, 9, 7, 8, 7]) == {7: 3, 8: 2, 9: 1}
output: from collections import Counter
  
  def findOccurrences(arr):
      return dict(Counter(arr))