input: Write a python function to square each element in a list.
  assert square_elements([1, 2, 3, 4, 5]) == [1, 4, 9, 16, 25]
  assert square_elements([6, 7, 8, 9, 10]) == [36, 49, 64, 81, 100]
  assert square_elements([2, 3, 5]) == [4, 9, 25]
output: def square_elements(lst):
      return [x ** 2 for x in lst]