@SuppressWarnings("unchecked")
    public final <T extends Properties> T getInstance(Class<T> propertyClass) {
        if (propertyClass.isAssignableFrom(this.getClass())) return (T) this;
        if (chained == null) return null;
        return chained.getInstance(propertyClass);
    }
Returns the first instance of the given class in this chain, or null if none
container-core/src/main/java/com/yahoo/processing/request/Properties.java