input: Write a function that takes a list of integers and returns a list of their squared values using list comprehension.
  assert squared_values([1, 2, 3, 5, 8, 13]) == [1, 4, 9, 25, 64, 169]
  assert squared_values([-2, 0, 3]) == [4, 0, 9]
  assert squared_values([]) == []
  assert squared_values([-1, -1, -1]) == [1, 1, 1]
output: def squared_values(lst):
      return [x**2 for x in lst]