
*** Original commit *** DataSource.open() throws if already opened. Update DataSource implementations to throw an error if open() is called when the DataSource is already open. *** PiperOrigin-RevId: 348783425
*** Original commit *** DataSource.open() throws if already opened. Update DataSource implementations to throw an error if open() is called when the DataSource is already open. *** PiperOrigin-RevId: 348783425