code: def format_size(size):
      
      units = ['B', 'KB', 'MB', 'GB']
      unit = ''
      n = size
      old_n = n
      value = size
      for i in units:
          old_n = n
          x, y = divmod(n, 1024)
          if x == 0:
              unit = i
              value = y
              break
  
          n = x
          unit = i
          value = old_n
      return str(value)+unit
docs: Convert size to XB, XKB, XMB, XGB
      :param size: length value
      :return: string value with size unit