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