remove TimeStamp import

csst_common/data_manager.py

@@ -33,7 +33,7 @@ from csst_dfs_api.sls.level2spectra import Level2SpectraApi as SlsLevel2DataApi
 from .logger import get_logger
 from .params import CSST_PARAMS as CP
 from .params import DFS_CONF
-from .time import now, TimeStamp
+from .time import now
 from .crds import CRDS
 from .dfs import DFS