def METHOD_NAME(self):
    """
    A Specviz helper (`~jdaviz.configs.specviz.helper.Specviz`) for the Jdaviz
    application that is wrapped by Specviz2d.
    """
    if not hasattr(self, '_specviz'):
        self._specviz = Specviz(app=self.app)
    return self._specviz