如何使用生成器迭代树结构？

I'm trying to figure out how to implement a function in a tree node which returns all its descendant leaves (whether direct or indirect). However, I don't want to pass a container in which the leaf nodes will be put recursively (the tree could be huge), instead I'd like to use a generator to iterate through the tree. I've tried a few approaches but none of them worked so far. This one is the closest I've come to a possible solution:I'm trying to figure out how to implement a fun