code: public <T> T get() {
      _fjtask.join();             // Block until top-level job is done
      T ans = (T) UKV.get(destination_key);
      remove();                   // Remove self-job
      return ans;
    }
docs: Blocks and get result of this job.
  <p>
  The call blocks on working task which was passed via {@link #start(H2OCountedCompleter)} method
  and returns the result which is fetched from UKV based on job destination key.
  </p>
  @return result of this job fetched from UKV by destination key.
  @see #start(H2OCountedCompleter)
  @see UKV