private void createRefActions() {
		referencesToAction = new ToggleDockingAction("References To", getName()) {
			@Override
			public void actionPerformed(ActionContext context) {
				if (referencesToAction.isSelected()) {
					refProvider.showReferencesTo();
					referencesToAction.setSelected(true);
					instructionsFromAction.setSelected(false);
					dataFromAction.setSelected(false);
				}
				// don't let the user de-click the button, since these buttons change in
				// response to each other, like a javax.swing.ButtonGroup set
				else {
					reselectAction(referencesToAction);
				}
			}
		};
		referencesToAction.setDescription("References To");
		referencesToAction.setSelected(true);
		referencesToAction.setToolBarData(
			new ToolBarData(new GIcon("icon.plugin.symboltable.references.to"), null));

		tool.addLocalAction(refProvider, referencesToAction);

		instructionsFromAction = new ToggleDockingAction("Instruction References From", getName()) {
			@Override
			public void actionPerformed(ActionContext context) {
				if (instructionsFromAction.isSelected()) {
					refProvider.showInstructionsFrom();
					referencesToAction.setSelected(false);
					instructionsFromAction.setSelected(true);
					dataFromAction.setSelected(false);
				}
				// don't let the user de-click the button, since these buttons change in
				// response to each other, like a javax.swing.ButtonGroup set
				else {
					reselectAction(instructionsFromAction);
				}
			}
		};
		instructionsFromAction.setDescription("Instructions From");
		instructionsFromAction.setSelected(false);
		instructionsFromAction.setToolBarData(
			new ToolBarData(new GIcon("icon.plugin.symboltable.instructions.from"), null));

		tool.addLocalAction(refProvider, instructionsFromAction);

		dataFromAction = new ToggleDockingAction("Data References From", getName()) {
			@Override
			public void actionPerformed(ActionContext context) {
				if (dataFromAction.isSelected()) {
					refProvider.showDataFrom();
					referencesToAction.setSelected(false);
					instructionsFromAction.setSelected(false);
					dataFromAction.setSelected(true);
				}
				// don't let the user de-click the button, since these buttons change in
				// response to each other, like a javax.swing.ButtonGroup set
				else {
					reselectAction(dataFromAction);
				}
			}
		};
		dataFromAction.setDescription("Data From");
		dataFromAction.setSelected(false);
		dataFromAction.setToolBarData(
			new ToolBarData(new GIcon("icon.plugin.symboltable.data.from"), null));

		tool.addLocalAction(refProvider, dataFromAction);
	}
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