private void doSetLocation(ProgramLocation location) {
		if (location == null) {
			setFunction(null);
			return;
		}

		if (currentProgram == null) {
			// This can happen when we were created to lock onto one location and then the program
			// for that location was closed.  Then, the user pressed the button to track location
			// changes, which means we will get here while setting the location, but our program
			// will have been null'ed out.
			currentProgram = plugin.getCurrentProgram();
			currentProgram.addListener(this);
		}

		// TODO Don't need the function - need the High Variable / High Function.
		Function function = plugin.getFunction(location);
		setFunction(function);
	}
A variable used to restrict open-ended operations, like expanding all nodes or filtering.
Ghidra/Features/DecompilerDependent/src/main/java/ghidra/app/plugin/core/decompiler/taint/TaintSliceTreeProvider.java