def seqfy(strs):
if not strs:<EOL><INDENT>return<EOL><DEDENT>result = "<STR_LIT>"<EOL>seq = <NUM_LIT:1><EOL>ss = strs.split("<STR_LIT:\n>")<EOL>for i in ss:<EOL><INDENT>if i:<EOL><INDENT>result = "<STR_LIT>".join([result, str(seq), "<STR_LIT:.>", i, "<STR_LIT:\n>"])<EOL>seq = seq + <NUM_LIT:1>            <EOL><DEDENT><DEDENT>return result<EOL>
序列化 字符串--->实际效果是，为字符串，添加行号，返回字符串
    Sampe usage:
        strs = ["", None, u"First-line\nSecond-line\nThird-line", u"没有换行符"]
        for s in strs:
            print "---"
            result = seqfy(s)
            print result
            print unseqfy(result)