@Override
	public default Class<Boolean> getValueClass() {
		return Boolean.class;
	}
Property manager that deals with properties that are of
"void" type, which is a marker for whether a property exists.
Object values returned are either {@link Boolean#TRUE} or null.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/util/VoidPropertyMap.java