pub trait Encoder<const LEN: usize>: Decoder<LEN> {
// Required methods
fn alphabet(&self) -> Alphabet<'_, LEN>;
fn encoded_len(&self, len: usize) -> Option<usize>;
fn encode_into<'a>(&self, dst: &'a mut [u8], src: &[u8]) -> &'a str;
// Provided method
fn encode(&self, src: &[u8]) -> String { ... }
}