input: Write a python function to check if two lists contain the same elements, regardless of order.
  assert is_equal([1, 2, 3], [3, 2, 1]) == True
  assert is_equal([1, 2, 3], [1, 2, 2]) == False
  assert is_equal([1, 2, 3], [1, 2, 3, 4]) == False
output: def is_equal(list1, list2):
      return sorted(list1) == sorted(list2)