@NonNull
    public <T> T getOrDefault(@NonNull Key<T> key) {
        return Objects.requireNonNull(this.get(key), "expected non-null value or defaultValue supplier");
    }
Returns the value in the context, or default value from the
typed key default value supplier if absent.
zuul-core/src/main/java/com/netflix/zuul/context/SessionContext.java