updated README.md

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## `data manager`

```python

import os

from csst.ms.data_manager import CsstMscDataManager

from csst.ms.backbone import CCD_ID_LIST

# initialize data manager

dm = CsstMscDataManager(

    ver_sim="C5.1", dir_l0="/data/sim_data/MSC_0000100", dir_l1="/home/user/L1Pipeline/msc/work")

# process all CCDs

dm.set_ccd_ids(CCD_ID_LIST)

print("----- available ccd_ids -----")

print(dm.available_ccd_ids)

for ccd_id in dm.target_ccd_ids:

    print("----- L0 images -----")

    print(dm.l0_ccd(ccd_id=ccd_id))

    print(os.path.exists(dm.l0_ccd(ccd_id=ccd_id)))

    print("----- L0 crs -----")

    print(dm.l0_crs(ccd_id=ccd_id))

    print(os.path.exists(dm.l0_ccd(ccd_id=ccd_id)))

    print("----- L0 input cat -----")

    print(dm.l0_cat(ccd_id=ccd_id))

    print(os.path.exists(dm.l0_cat(ccd_id=ccd_id)))

    print("----- L0 input log -----")

    print(dm.l0_log(ccd_id=ccd_id))

    print(os.path.exists(dm.l0_log(ccd_id=ccd_id)))

    print("----- L1 images -----")

    print(dm.l1_ccd(ccd_id, post="img.fits"))

```

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