public Set<InternalDistributedMember> getAllNodes() {
    Set<InternalDistributedMember> result = getRegionAdvisor().adviseDataStore(true);
    if (isDataStore()) {
      result.add(getDistributionManager().getId());
    }
    return result;
  }
Test Method: Get all {@link InternalDistributedMember}s known by this instance of the
PartitionedRegion. Note: A member is recognized as such when it partiticpates as a "data
store".

@return a {@code HashSet} of {@link InternalDistributedMember}s or an empty {@code HashSet}
geode-core/src/main/java/org/apache/geode/internal/cache/PartitionedRegion.java