def METHOD_NAME(self):
    if self._var_cache is None:
        script = self.var.get('_prepare', _eval=False, default='') + \
            self.var.get('_run', _eval=False, default='')
        self._var_cache = [
            (key, None) for key in self._extract_assignments(script)]
    return super().METHOD_NAME() + self._var_cache