input: Write a python function to check if an array contains duplicates.
  assert check_duplicates([3, 5, 2, 4, 2]) == True
  assert check_duplicates([1, 2, 3, 4, 5]) == False
  assert check_duplicates([10, 20, 30, 20, 40]) == True
output: def check_duplicates(arr):
      return len(arr) != len(set(arr))