input: Write a function to generate a list of squared values using list comprehension from a given list. The function should take a list of integers as its input and return a new list containing the squared values of the input list.
  assert squared_values([1, 2, 3, 5, 8, 13])==[1, 4, 9, 25, 64, 169]
  assert squared_values([])==[]
  assert squared_values([0, -1, -2])==[0, 1, 4]
output: def squared_values(lst):
      return [x**2 for x in lst]