public BigInteger getIndex() {
			return layout.getIndex();
		}
Returns the index of the layout as defined by the client code. The only requirements for
indexes is that the index for a layout is always bigger then the index of the previous
layout.
@return the index of the layout as defined by the client code.
Ghidra/Framework/Docking/src/main/java/docking/widgets/fieldpanel/AccessibleFieldPanelDelegate.java