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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 _add_current_quay_tag(repo, container_tags):
 """Lookup the current quay tag for the repository, adding to repo string. Enables generation of CWL explicitly tied to revisions. """

    if ':' in repo:
        return repo, container_tags
    try:
        latest_tag = container_tags[repo]
    except KeyError:
        repo_id = repo[repo.find('/') + 1:]
        tags = requests.request("GET", "https://quay.io/api/v1/repository/" + repo_id).json()["tags"]
        latest_tag = None
        latest_modified = None
        for tag, info in tags.items():
            if latest_tag:
                if (dateutil.parser.parse(info['last_modified']) > dateutil.parser.parse(latest_modified)
                      and tag != 'latest'):
                    latest_modified = info['last_modified']
                    latest_tag = tag
            else:
                latest_modified = info['last_modified']
                latest_tag = tag
        container_tags[repo] = str(latest_tag)
    latest_pull = repo + ':' + str(latest_tag)
    return latest_pull, container_tags