code: public static Aggregator get(final String name) {
      final Aggregator agg = aggregators.get(name);
      if (agg != null) {
        return agg;
      }
      throw new NoSuchElementException("No such aggregator: " + name);
    }
docs: Returns the aggregator corresponding to the given name.
  @param name The name of the aggregator to get.
  @throws NoSuchElementException if the given name doesn't exist.
  @see #set