input: Write a function to generate a list comprehension that produces the squared values of a given list. If the input list is empty, return an empty list.
  assert square_list([1, 2, 3, 5, 8, 13])==[1, 4, 9, 25, 64, 169]
  assert square_list([])==[]
  assert square_list([4, 9, 16])==[16, 81, 256]
output: def square_list(lst):
      return [x**2 for x in lst]