private void updateIncomingReferencs(Function function) {
		GTreeNode rootNode = null;
		if (function == null) {
			rootNode = new EmptyRootNode();
		}
		else {
			rootNode = new IncomingCallsRootNode(currentProgram, function, function.getEntryPoint(),
				callTreeOptions);
		}
		incomingTree.setRootNode(rootNode);
	}
A variable used to restrict open-ended operations, like expanding all nodes or filtering.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/calltree/CallTreeProvider.java