pub fn accepted(key: &str, value: &str) -> Result<String>Expand description
value as showFormat, writeFormat or autoDownload takes it: in
lower case, and an error where it is not one music21 allows. Any other
preference takes any value, and value comes back as it was given.
use music21::environment::accepted;
assert_eq!(accepted("showFormat", "MusicXML").unwrap(), "musicxml");
assert_eq!(
accepted("autoDownload", "asdf").unwrap_err().to_string(),
"Environment error: asdf is not an acceptable value for preference: autoDownload"
);