input: Write a python function to double the numbers in a list.
  assert double_numbers([2, 4, 6, 8])==[4, 8, 12, 16]
  assert double_numbers([1, 3, 5, 7])==[2, 6, 10, 14]
  assert double_numbers([10, 20, 30, 40])==[20, 40, 60, 80]
output: def double_numbers(numbers):
      return [number * 2 for number in numbers]