code: def GetUnreachableHosts(hostnames, ssh_key):
    
    ssh_status = AreHostsReachable(hostnames, ssh_key)
    assert(len(hostnames) == len(ssh_status))
    nonresponsive_hostnames = [host for (host, ssh_ok) in
                               zip(hostnames, ssh_status) if not ssh_ok]
    return nonresponsive_hostnames
docs: Returns list of hosts unreachable via ssh.