code: public void emitAll(KeyValueHandler out) {
      for (Entry<String, SortedSet<Object>> e : map.entrySet()) {
        // Remember that tags can exist without values.
        String key = e.getKey();
        Set<Object> values = e.getValue();
        if (!values.isEmpty()) {
          for (Object value : values) {
            out.handle(key, value);
          }
        } else {
          out.handle(key, null);
        }
      }
    }
docs: Emits all the key/value pairs of this Tags instance to the given consumer.