Alternative to the "_" entry point.

[andrw3000]

Suggestion:

We could do something like LangGraph where they have two

from uncertainty_engine_sdk import START, END

object that index the global input and termination points of a graph. It stands out a bit more in the editor (it's blue!) against '_' say.

This would make is clearer to look at. It would also allow us to bake in some internal logic to control the plotting etc.

It's used in here, for example... https://docs.smith.langchain.com/evaluation/how_to_guides/langgraph