Function db_value 

pub fn db_value(
    conn: i64,
    basis_tx: i64,
    as_of: Option<i64>,
    since: Option<i64>,
) -> Value

Build a db-value mino map: {:mentat.store/db true :mentat.store/conn N :mentat.store/basis-tx T :mentat.store/as-of A :mentat.store/since S}.