input: Write a python function to generate a list of squares for a given list of numbers.
  assert generate_squares([1, 2, 3, 4, 5, 6]) == [1, 4, 9, 16, 25, 36]
  assert generate_squares([0, -1, -2, -3]) == [0, 1, 4, 9]
  assert generate_squares([10, 11, 12]) == [100, 121, 144]
output: def generate_squares(numbers):
      return [x**2 for x in numbers]