How to use different envs one by one through Python scripts

Hello, I meet a little problem.
I use Isaac Sim to train my DRL Agent, it’s training is related to several maps. Now I want to train the agent first in map1, then map2, map3 and etc. The workflow of my steps are just like below.

my_env = CustomEnv(map1)
## do some model learning here

my_env = CustomEnv(map2)
## do some model learning here

Then I face a problem that whenever my_env.close() is called, the Python script will definitely exit, so I have no change to get into map2.
What’s inside my_env.close() is like below.

self._simulation_app = SimulationApp({"headless":self._headless,"anti_aliasing":0})
## other codes
    def close(self, seed=None):

Thanks in advance for any solutions and advice!!