code: def _open_connection(self):
          
          if self._connection:
              try:
                  self._connection.close()
              except Exception:
                  pass
  
          db = self._get_db()
          self._connection = db.open()
  
          self._connection.onCloseCallback(self._on_close_callback)
docs: Open the connection to the database based on the configuration file.