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