@Override
	protected void locationChanged(ProgramLocation loc) {
		for (CallTreeProvider provider : providers) {
			provider.setLocation(loc);
		}
	}
Assuming a function <b>foo</b>, this plugin will show:
 1) all callers of <b>foo</b> 
 2) all functions which reference <b>foo</b>
 3) all callees of <b>foo</b>
 4) all functions referenced by <b>foo</b>.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/calltree/CallTreePlugin.java