pub trait ToJSON {
// Required method
fn append_as_json_string(&self, buf: &mut String);
// Provided method
fn as_json_string(&self) -> String { ... }
}
pub trait ToJSON {
// Required method
fn append_as_json_string(&self, buf: &mut String);
// Provided method
fn as_json_string(&self) -> String { ... }
}