refactor: The first refactored version for sdk release (#907)

Co-authored-by: chengfangyin2 <chengfangyin3@jd.com>

dbgpt/storage/metadata/_base_dao.py

@@ -0,0 +1,25 @@
+from typing import TypeVar, Generic, Any
+from sqlalchemy.orm import sessionmaker
+
+T = TypeVar("T")
+
+
+class BaseDao(Generic[T]):
+    def __init__(
+        self,
+        orm_base=None,
+        database: str = None,
+        db_engine: Any = None,
+        session: Any = None,
+    ) -> None:
+        """BaseDAO, If the current database is a file database and create_not_exist_table=True, we will automatically create a table that does not exist"""
+        self._orm_base = orm_base
+        self._database = database
+
+        self._db_engine = db_engine
+        self._session = session
+
+    def get_session(self):
+        Session = sessionmaker(autocommit=False, autoflush=False, bind=self._db_engine)
+        session = Session()
+        return session