code: def encode(cls, text):
          
          text_length = len(text)
          # 计算需要填充的位数
          amount_to_pad = cls.block_size - (text_length % cls.block_size)
          if amount_to_pad == 0:
              amount_to_pad = cls.block_size
          # 获得补位所用的字符
          pad = to_binary(chr(amount_to_pad))
          return text + pad * amount_to_pad
docs: 对需要加密的明文进行填充补位
          @param text: 需要进行填充补位操作的明文
          @return: 补齐明文字符串