pub trait BlockListRequired<'a, T>{
// Required method
fn block_list(&self) -> &'a BlockList<T>;
// Provided method
fn to_string(&self) -> String { ... }
}
pub trait BlockListRequired<'a, T>{
// Required method
fn block_list(&self) -> &'a BlockList<T>;
// Provided method
fn to_string(&self) -> String { ... }
}