@Override
			public void actionPerformed(ActionContext context) {
				Object contextObject = context.getContextObject();
				GTree gTree = (GTree) contextObject;
				GTreeNode rootNode = gTree.getViewRoot();
				List<GTreeNode> children = rootNode.getChildren();
				for (GTreeNode child : children) {
					gTree.collapseAll(child);
				}
			}
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