You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: storage.rs
    path of file: ./repos/snarkOS/node/bft/src/helpers
    
    the code of the file until where you have to start completion: // Copyright (C) 2019-2023 Aleo Systems Inc.
// This file is part of the snarkOS library.

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
//
    
    pub fn get_certificates_for_round(&self, round: u64) -> IndexSet<BatchCertificate<N>> {
        // The genesis round does not have batch certificates.
        if round == 0 {
            return Default::default();
        }
        // Retrieve the certificates.
        if let Some(entries) = self.rounds.read().get(&round) {
            let certificates = self.certificates.read();
            entries.iter().flat_map(|(certificate_id, _, _)| certificates.get(certificate_id).cloned()).collect()
        } else {
            Default::default()
        }
    }