t_json indicates that:
        a.) Send header Accept: 'application/json'
        b.) Instead of raw content, return json.loads(content)
    retry_delays is None or an iterator (including list or tuple)
        If it is None, no retries will be done.
        If it is an iterator, each value is number of seconds to delay before
        retrying.  For example, retry_delays=(3,5) means to try up to 3
        times, with a 3s delay after first failure and 5s delay after second.
        Retries will not be done on 404.)