@SuppressWarnings("unchecked")
    @Nullable public <T> T get(@NonNull Key<T> key) {
        T value = (T) typedMap.get(key);
        if (value == null) {
            value = key.defaultValue();
        }

        return value;
    }
Returns the value in the context, or {@code null} if absent.
zuul-core/src/main/java/com/netflix/zuul/context/SessionContext.java