update README.md

README.md

 # csst-dag
 
 CSST pipeline DAG.
+
+
+```python
+# 筛选出所有符合条件的 DAG
+from csst_dag.dag import CSST_DAG_LIST
+
+assert CSST_DAG_LIST.match(obsid="11009101682009", chipid="01") == ["csst-msc-l1-sls"]
+```
+```python
+# 验证某个DAG是否
+from csst_dag.dag import CSST_DAG_LIST
+
+dag = CSST_DAG_LIST[0]
+dag.pprint()
+
+dag.match(obsid="11009101682009", chipid="01") # 返回True
+dag.match(obsid="10109101682009", chipid="12") # 返回True
+```
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