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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_bundle_for_cn(cn, relation_name=None):
 """Extract certificates for the given cn. :param cn: str Canonical Name on certificate. :param relation_name: str Relation to check for certificates down. :returns: Dictionary of certificate data, :rtype: dict. """

    entries = get_requests_for_local_unit(relation_name)
    cert_bundle = {}
    for entry in entries:
        for _cn, bundle in entry['certs'].items():
            if _cn == cn:
                cert_bundle = {
                    'cert': bundle['cert'],
                    'key': bundle['key'],
                    'chain': entry['chain'],
                    'ca': entry['ca']}
                break
        if cert_bundle:
            break
    return cert_bundle