@Override
				public boolean isEnabledForContext(ActionContext context) {
					Object contextObject = context.getContextObject();
					if (!(contextObject == outgoingTree)) {
						return false;
					}

					GTree gTree = (GTree) contextObject;
					if (gTree.getSelectionPaths().length != 1) {
						return false;
					}

					TreePath path = gTree.getSelectionPath();
					if (path == null) {
						return false;
					}

					GTreeNode node = (GTreeNode) path.getLastPathComponent();
					return (node instanceof CallNode);
				}
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