Inverses of mixin predicates don't establish an is_a path to a "root" mixin

[sierra-moxon]

From @colleenXu :

Some of the new "treats"-related predicates are mixins that the other predicates are mapped to: promotes condition, treats, treats or applied or studied to treat. I thought their inverses would be the same (and just map to the equivalent inverse predicates), but: -

• condition promoted by isn't a mixin
• treated by and subject of treatment application or study for treatment by are set as mixins, but other predicates aren't mapped to them
• At the moment, I don't think it'll be a breaking problem. But I do think our team will need to be aware/account for it during the ARA implementation of "treats refactor", by explicitly including all "treats"-related predicates in a template that we want used.

Ex: if we flip treats or applied or studied to treat to subject of treatment application or study for treatment by for execution, the predicate isn't a mixin that'll expand to all "treats-related" predicates the same way the canonical predicate will.