def init_db(self, txn=None): """Connect to database and create tables. Parameters ---------- txn : sa.engine.Connection, optional The transaction to execute in. If this is not provided, a new transaction will be started with the engine provided. Returns ------- metadata : sa.MetaData The metadata that describes the new assets db. """ with ExitStack() as stack: if txn is None: txn = stack.enter_context(self.engine.begin()) tables_already_exist = self._all_tables_present(txn) # Create the SQL tables if they do not already exist. metadata.create_all(txn, checkfirst=True) if tables_already_exist: check_version_info(txn, version_info, ASSET_DB_VERSION) else: write_version_info(txn, version_info, ASSET_DB_VERSION)