pub trait RuntimeVarDb {
// Required methods
fn try_get_var(&mut self, var_name: &str) -> Option<(Vec<u8>, bool)>;
fn set_var(&mut self, var_name: &str, is_secret: bool, value: Vec<u8>);
// Provided method
fn get_var(&mut self, var_name: &str) -> (Vec<u8>, bool) { ... }
}