static <T, E extends Enum<E>> ToEnumNullable<T, E>
    of(Class<E> enumClass, Function<T, E> lambda) {
        return new ToEnumNullableImpl<>(enumClass, lambda);
    }
Returns a typed {@code ToEnumNullable<T>} using the provided
{@code lambda}.

@param <T> type to extract from
@param <E> enum type
@param lambda to convert
@param enumClass class for the enum
@return a typed {@code ToEnumNullable<T>} using the provided
        {@code lambda}

@throws NullPointerException if the provided {@code lambda} is
{@code null}
runtime-parent/runtime-compute/src/main/java/com/speedment/runtime/compute/ToEnumNullable.java