<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def json(self, json_string=None):
 """ Convenience method allowing easy dumping to and loading from json. """

        if json_string is not None:
            return self.__init__(loads(json_string))
        dump = self
        if isinstance(self, HAR.log):
            dump = {"log": dump}
        return dumps(dump, default=lambda x: dict(x))