convert_state_name (and other converters) return input string if no match #3
Description
If you call ModelUN.convert_state_name("some non-state name") you will get back "Some Non-State Name" as the result with no way other than comparing your input string to the result to know if any actual conversion happened. I would expect it to return nil if it's unable to convert the string to anything.
Based on looking at the ModelUN code, it seems like the other converters behave the same way.