如何在Alexa技能中使用特定于会话的变量？

I'm developing a fact skill for Alexa using their SpaceGeek template. The template itself is very straight forward, but I'm trying to improve it by making sure the facts used will not come up again in the same session. So I delete the element after it is used. However, now it comes to a problem that, those elements deleted in the session won't even come up in future sessions. So I assume the global variable stays in the backend and thus created a copy-array as below. But it still won't work. So after using all the facts once, I'll always get "That's all the facts we have for now". Even if I start a new session. Any help will be appreciated.I'm developing a fact skill for Alexa using the