boolean isBusy() {
		return domainObjectWorker.isBusy() || symProvider.isBusy() || refProvider.isBusy();
	}
Tells a plugin that it is no longer needed.
The plugin should remove itself from anything that
it is registered to and release any resources.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/symtable/SymbolTablePlugin.java