Function is_standard_name 

pub fn is_standard_name(name: &str) -> bool

Whether a name is one the vocabulary knows, by its unique name or by its namespaced one: music21’s isStandardName. A name of music21’s own older vocabulary – a work id or its abbreviation – is not one of these, as music21’s answer is not either.

use music21::metadata::is_standard_name;

assert!(is_standard_name("librettist"));
assert!(is_standard_name("marcrel:LBT"));
assert!(!is_standard_name("average duration"));
assert!(!is_standard_name("soundtracker:SampleName"));