public synchronized long getLastPropertyIndex() throws NoSuchIndexException {
		// -1 should be the highest possible address
		if (hasProperty(-1)) {
			return -1;
		}
		return getPreviousPropertyIndex(-1);
	}
Get the last index where a property value exists.
@exception NoSuchIndexException
                  thrown if there is no address having the property value.
Ghidra/Framework/Generic/src/main/java/ghidra/util/map/ValueMap.java