input: Write a function to generate a list of squared values of a given list using list comprehension. The function should take one argument, the list to be squared, and return the list of squared values.
  assert squared_values([1, 2, 3, 5, 8, 13])==[x*x for x in [1, 2, 3, 5, 8, 13]]
  assert squared_values([2, 4, 6])==[4, 16, 36]
  assert squared_values([0, -1, -2])==[0, 1, 4]
  assert squared_values([])==[]
  assert squared_values([-3, -2, -1, 0, 1, 2, 3])==[9, 4, 1, 0, 1, 4, 9]
output: def squared_values(lst):
      return [x*x for x in lst]