input: Write a python function to modify a list of numbers based on whether they are even or odd, using the modify_number function.
  assert modify_list([1, 2, 3, 4, 5, 6]) == [0, 4, 2, 8, 4, 12]
  assert modify_list([10, 11, 12, 13]) == [20, 10, 24, 12]
  assert modify_list([7, 8, 9]) == [6, 16, 8]
output: def modify_number(n):
      if n % 2 == 0:
          return n * 2
      else:
          return n - 1
  
  def modify_list(lst):
      return [modify_number(n) for n in lst]