Function resolve_one 

fn resolve_one(code: &str) -> Result<Arc<dyn Calendar>, CalendarParseError>

Resolves a single token to a calendar: a bare FpML code (or alias) yields the jurisdiction settlement calendar; a qualified BASE.SUFFIX code (or a market alias such as nyse) yields the market calendar. A calendar ingested under the code — or under the canonical code an alias spells — answers first.