How to define class, method and property in BehaviorContext that can be used in Lua Script

I am newer to Lumberyard. I want to define a class in C++, and I can use the methods and property that defined in the class when I write my lua Script.
I write my C++ code according to the guide Behavior Context - Lumberyard User Guide . I create a Gem that named GemDemo and I enable it in my project. And I define Class and Property in BehaviorContext, But I can not see my class in Lua Editor

C++ code

Lua Editor