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: old_events.rs
    path of file: ./repos/krill/src/upgrades/pre_0_10_0
    
    the code of the file until where you have to start completion: use std::{
    collections::HashMap,
    convert::{TryFrom, TryInto},
    fmt,
};

use bytes::Bytes;
use rpki::{
    ca::{
        idcert::IdCert,
        idexchange::{CaHandle, ChildHandle, ParentHandle, PublisherHandle, RepoInfo, ServiceUri},
        pr
    
    fn try_from(old: OldChildCertificateUpdates) -> Result<Self, UpgradeError> {
        let mut issued: Vec<IssuedCertificate> = vec![];
        let mut suspended: Vec<SuspendedCert> = vec![];
        let mut unsuspended: Vec<UnsuspendedCert> = vec![];

        for old_delegated in old.issued.into_iter() {
            issued.push(old_delegated.try_into()?);
        }

        for old_suspended in old.suspended.into_iter() {
            suspended.push(old_suspended.try_into()?);
        }

        for old_unsuspended in old.unsuspended.into_iter() {
            unsuspended.push(old_unsuspended.try_into()?);
        }

        Ok(ChildCertificateUpdates::new(
            issued,
            old.removed,
            suspended,
            unsuspended,
        ))
    }