Function try_commit 

pub fn try_commit(
    double_cert: &DoubleCertificate,
    store: &dyn BlockStore,
    app: &dyn Application,
    last_committed_height: &mut Height,
) -> Result<Vec<Block>>

Execute the two-chain commit rule: When we get C_v(C_v(B_k)), commit the inner QC’s block and all uncommitted ancestors