code: public void computeRemainingTrailers() {
          if (tc.isEntryEnabled()) {
              Tr.entry(tc, "computeRemainingTrailers");
          }
          Iterator<HeaderKeys> knowns = this.knownTGs.keySet().iterator();
          while (knowns.hasNext()) {
              HeaderKeys key = knowns.next();
              setHeader(key, this.knownTGs.get(key).generateTrailerValue(key, this));
          }
          if (tc.isEntryEnabled()) {
              Tr.exit(tc, "computeRemainingTrailers");
          }
      }
docs: Compute all deferred headers.
  
  <p>
  All <code>HttpTrailerGenerator</code> will be called upon to create the value for their respective header. The values they create will automatically be added to the
  Trailer-based <code>BNFHeaders</code> object for immediate serialization.
  </p>