code: def start_app(self, bundle_id):
          
          # if self._session is not None:
          #     self.stop_app()
          self._bundle_id = bundle_id
          self._session = self._wda.session(bundle_id)
          return self._session
docs: Start an application
          Args:
              - bundle_id: (string) apk bundle ID
  
          Returns:
              WDA session object