func_code: def swap_first_last(a, first, last):
      if first >= last:
          return
      a[first], a[last] = a[last], a[first]
      first += 1
      last -= 1
      swap_first_last(a, first, last)
  
  
  def reverse_list(a):
      swap_first_last(a, 0, len(a) - 1)
      return a