Function encode 

pub fn encode(
    seq: u64,
    at: &str,
    action: &str,
    actor: &Actor<'_>,
    subject: Value,
    request: Option<&SignedRequest<'_>>,
) -> Vec<u8> 

Encodes one leaf as VERSION’s compact JSON, in the field order the design shows: v, seq, at, action, actor, subject, request.

This is the exact byte sequence that gets hashed, stored, and exported — see the module docs.