Function that will be spawned to fetch processed image
    from the output queue and write to the .rec file.
    Parameters
    ----------
    q_out: queue
    fname: string
    working_dir: string

def write_worker(q_out, fname, working_dir):
    """Function that will be spawned to fetch processed image
    from the output queue and write to the .rec file.
    Parameters
    ----------
    q_out: queue
    fname: string
    working_dir: string
    """
    pre_time = time.time()
    count = 0
    fname = os.path.basename(fname)
    fname_rec = os.path.splitext(fname)[0] + '.rec'
    fname_idx = os.path.splitext(fname)[0] + '.idx'
    record = mx.recordio.MXIndexedRecordIO(os.path.join(working_dir, fname_idx),
                                           os.path.join(working_dir, fname_rec), 'w')
    buf = {}
    more = True
    while more:
        deq = q_out.get()
        if deq is not None:
            i, s, item = deq
            buf[i] = (s, item)
        else:
            more = False
        while count in buf:
            s, item = buf[count]
            del buf[count]
            if s is not None:
                record.write_idx(item[0], s)

            if count % 1000 == 0:
                cur_time = time.time()
                print('time:', cur_time - pre_time, ' count:', count)
                pre_time = cur_time
            count += 1