in pyo3_special_method_derive_example/src/lib.rs [25:32]
fn from_str(s: &str) -> Result<Self, Self::Err> {
match s.to_lowercase().as_str() {
"paris" => Ok(CityName::Paris),
"london" => Ok(CityName::London),
"new york" => Ok(CityName::NewYork),
_ => Err(()),
}
}