Tools for backdoor vs non-backdoor paths

[malcolmbarrett]

I think it would be handy to be able to add a column and aesthetic based on types of paths, e.g. "biasing" vs "causal" in dagitty or "chain" vs "non-chain" -- basically, indicating which paths are open, non-causal* paths vs direct causal paths

*(I'm not quite sure the language to use yet as backdoor paths are also causal, just not for the question you're analyzing)

I need to think about the goals and API a bit