def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def _swdb_environment_install(self, env_id, pkg_types, groups):
        swdb_env = self._create_swdb_environment(env_id, pkg_types, groups)

        if swdb_env is not None:
            self._base.history.env.install(swdb_env)