code: public void push(Collector collector, String job) throws IOException {
      CollectorRegistry registry = new CollectorRegistry();
      collector.register(registry);
      push(registry, job);
    }
docs: Pushes all metrics in a Collector, replacing all those with the same job and no grouping key.
  <p>
  This is useful for pushing a single Gauge.
  <p>
  This uses the PUT HTTP method.