pub trait MessageExt {
// Required methods
fn extract_plain_text(&self) -> String;
fn is_plain_text(&self) -> bool;
// Provided method
fn extract_if_plain_text(&self) -> Option<String> { ... }
}pub trait MessageExt {
// Required methods
fn extract_plain_text(&self) -> String;
fn is_plain_text(&self) -> bool;
// Provided method
fn extract_if_plain_text(&self) -> Option<String> { ... }
}