@Override
	public DBCachedObjectStoreKeySubSet subSet(Long fromElement, boolean fromInclusive,
			Long toElement, boolean toInclusive) {
		KeySpan span = KeySpan.sub(fromElement, fromInclusive, toElement, toInclusive, direction);
		return new DBCachedObjectStoreKeySubSet(store, errHandler, lock, direction, span);
	}
This provides the implementation of {@link Map#keySet()} for {@link DBCachedObjectStore#asMap()}
Ghidra/Debug/ProposedUtils/src/main/java/ghidra/util/database/DBCachedObjectStoreKeySet.java