How to stop people getting confused when inspecting ancestors tree sequences?

[hyanwong]

@szhan was inspecting his ancestors tree sequences, and getting understandably confused because e.g. it had a number of singletons (dues to the fact that the ancestors are marked as samples, so some of those ancestors have a unique allele). I can see other cases where the (necessary) oddity of having all the internal nodes marked as samples will confuse people. Is there any obvious way to flag this up programmatically to avoid confusion? I can't think of anything obvious, to be honest - there's (deliberately?) no detectable difference between a normal tree sequence and an ancestors tree sequence, right? I seem to recall there were good reasons not to e.g. make an ancestors TS a derived python class with some slightly different methods.

[jeromekelleher]

That would be quite hard. Perhaps the simplest thing would be to add some top-level metadata saying this, which gets displayed when people view it as print(ts) or in a notebook?