input: Write a python function to compute the square of each element in a list.
  assert squares([1, 2, 3]) == [1, 4, 9]
  assert squares([4, 5, 6]) == [16, 25, 36]
  assert squares([0, 1, 2]) == [0, 1, 4]
output: def squares(lst):
      return [x ** 2 for x in lst]