pub trait InputValueDefinition: HasDirectives {
type InputType: InputType;
type Value: ConstValue;
// Required methods
fn description(&self) -> Option<&str>;
fn name(&self) -> &str;
fn type(&self) -> &Self::InputType;
fn default_value(&self) -> Option<&Self::Value>;
// Provided method
fn is_required(&self) -> bool { ... }
}