def header_output(self):
result = []<EOL>for key in self.keys():<EOL><INDENT>result.append(key + '<STR_LIT:=>' + self.get(key).value)<EOL><DEDENT>return '<STR_LIT>'.join(result)<EOL>
只输出cookie的key-value字串.

        比如: HISTORY=21341; PHPSESSION=3289012u39jsdijf28; token=233129