pub trait ValueStore {
// Required methods
fn value_opt<T>(&self, id: T) -> Option<&ValueData>
where T: Into<ValueId>;
fn update<T, U>(&mut self, id: T, value: U) -> Option<ValueData>
where T: Into<ValueId>,
U: Into<ValueData>;
// Provided methods
fn value(&self, id: impl Into<ValueId>) -> &ValueData { ... }
fn integer_value<T>(&self, id: T) -> Option<i64>
where T: Into<ValueId> { ... }
fn float_value<T>(&self, id: T) -> Option<f64>
where T: Into<ValueId> { ... }
fn str_value<T>(&self, id: T) -> Option<&String>
where T: Into<ValueId> { ... }
}