input: Write a function to find the intersection of two arrays.
  assert intersection_arr([1, 2, 3, 4, 5], [3, 4, 5, 6, 7]) == [3, 4, 5]
  assert intersection_arr([10, 20, 30], [20, 30, 40]) == [20, 30]
  assert intersection_arr([7, 8, 9], [10, 11, 12]) == []
output: def intersection_arr(arr1, arr2):
      return list(set(arr1) & set(arr2))