public Set keySet(boolean allowTombstones) {
    checkReadiness();
    checkForNoAccess();
    return new EntriesSet(this, false, IteratorType.KEYS, allowTombstones);
  }
return a set of the keys in this region

@param allowTombstones whether destroyed entries should be included
@return the keys
geode-core/src/main/java/org/apache/geode/internal/cache/LocalRegion.java