docs: def get_app(self, reference_app=None):
          """Helper method that implements the logic to look up an
          application."""
  
          if reference_app is not None:
              return reference_app
  
          if current_app:
              return current_app._get_current_object()
  
          if self.app is not None:
              return self.app
  
          raise RuntimeError(
              'No application found. Either work inside a view function or push'
              ' an application context. See'
              ' http://flask-sqlalchemy.pocoo.org/contexts/.'
          )