void addColocatedBucket(String region, Bucket b) {
    if (!getColocatedBuckets().containsKey(region)) {
      getColocatedBuckets().put(region, b);
      changeLoad(b.getLoad());
      changePrimaryLoad(b.getPrimaryLoad());
      changeBytes(b.getBytes());
      addOfflineMembers(b.getOfflineMembers());

      // Update the load on the members hosting this bucket
      // to reflect the fact that the bucket is larger now.
      for (Member member : getMembersHosting()) {
        MemberRollup rollup = (MemberRollup) member;
        float primaryLoad = 0;
        if (getPrimary() == member) {
          primaryLoad = b.getPrimaryLoad();
        }
        rollup.updateLoad(b.getLoad(), primaryLoad, b.getBytes());
      }
    }
  }
Represents the sum of all of colocated buckets with a given bucket id.
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/rebalance/model/BucketRollup.java