code: public Map<Group, List<ServerMonitoringStatistics>> getMonitoringStatsAsMap(List<Group> groups, ServerMonitoringFilter config) {
          Map<Group, List<ServerMonitoringStatistics>> result = new HashMap<>(groups.size());
          groups.stream()
              .forEach(group -> result.put(group, getMonitoringStats(group, config)));
  
          return result;
      }
docs: Retrieve the resource usage of servers within a group hierarchy statistics.
  @param groups the list of Group references
  @param config configuration for statistics entries
  @return the statistics map