How do you use 3rd-party analytics APIs?

[matthew-dean]

Platforms like Gtag have an API that supports things like retrieving the generated clientId, which we need for passing the GA id to segment. The code looks something like:

  gtag('get', GA_ID, 'client_id', clientId => {
      gaClientId = clientId;
      sendClientToSegment();
  });

However, I don't see anything in Analytics or the Gtag plugin that supports this. Is that true?