func_code: def swap(a, x, y):
      tmp = a[x]
      a[x] = a[y]
      a[y] = tmp
      return a
  
  
  def reverse(a):
      i = 0
      j = len(a) - 1
      while i < len(a) / 2:
          swap(a, i, j)
          i += 1
          j -= 1
      return a