src/vs/editor/contrib/gotoSymbol/browser/goToCommands.ts/SymbolNavigationAnchor/is
class SymbolNavigationAnchor:	static is(thing: any): thing is SymbolNavigationAnchor {
		if (!thing || typeof thing !== 'object') {
			return false;
		}
		if (thing instanceof SymbolNavigationAnchor) {
			return true;
		}
		if (corePosition.Position.isIPosition((<SymbolNavigationAnchor>thing).position) && (<SymbolNavigationAnchor>thing).model) {
			return true;
		}
		return false;
	}