private boolean handleSymbolAddedRemoved(DomainObjectChangedEvent ev,
			boolean isRebuildingGraph) {
		if (isRebuildingGraph) {
			rebuildGraphUpdateManager.updateLater();
			return true;
		}

		//
		// Do we need to modify the affected vertex?
		//
		for (DomainObjectChangeRecord record : ev) {
			EventType eventType = record.getEventType();
			if (eventType == ProgramEvent.SYMBOL_ADDED) {
				handleSymbolAdded(record);
			}
			else if (eventType == ProgramEvent.SYMBOL_REMOVED) {
				handleSymbolRemoved(record);
			}
		}

		return false;
	}
Returns true when something destructive has happened to the data upon which the graph has
created, like a memory block move.
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/FGProvider.java