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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def from_json(cls, json_info):
 """Build a Result instance from a json string."""

        if json_info is None:
            return None
        return ResultRecord(
            trial_id=json_info["trial_id"],
            timesteps_total=json_info["timesteps_total"],
            done=json_info.get("done", None),
            episode_reward_mean=json_info.get("episode_reward_mean", None),
            mean_accuracy=json_info.get("mean_accuracy", None),
            mean_loss=json_info.get("mean_loss", None),
            trainning_iteration=json_info.get("training_iteration", None),
            timesteps_this_iter=json_info.get("timesteps_this_iter", None),
            time_this_iter_s=json_info.get("time_this_iter_s", None),
            time_total_s=json_info.get("time_total_s", None),
            date=json_info.get("date", None),
            hostname=json_info.get("hostname", None),
            node_ip=json_info.get("node_ip", None),
            config=json_info.get("config", None))