Question: When there are no valid taxons, we accept all taxons

[dougli1sqrd]

In _validate_taxon() if in the config there are no valid taxons, or self.config.valid_taxa is None we accept all taxons. This seems counterintuitive, since wouldn't that mean that there does not exist a taxon that is valid?

[cmungall]

It's perhaps unfortunate that the python reserved term in None, but really we mean unset, ie client does not care. How else should we indicate this? We could do a string like * (ugh), force the user to enumerate all possibilities (not desirable) or use a scala-esque object NotSet | List which is not very pythonesque....

[cmungall]

We'll retain the current behavior - an empty whitelist means accept all