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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 _build_job_meta(cls, job_dir):
 """Build meta file for job. Args: job_dir (str):
 Directory path of the job. Return: A dict of job meta info. """

        meta_file = os.path.join(job_dir, JOB_META_FILE)
        meta = parse_json(meta_file)

        if not meta:
            job_name = job_dir.split("/")[-1]
            user = os.environ.get("USER", None)
            meta = {
                "job_id": job_name,
                "job_name": job_name,
                "user": user,
                "type": "ray",
                "start_time": os.path.getctime(job_dir),
                "end_time": None,
                "best_trial_id": None,
            }

        if meta.get("start_time", None):
            meta["start_time"] = timestamp2date(meta["start_time"])

        return meta