static <T> ToIntNullable<T> of(Function<T, Integer> lambda) {
        requireNonNull(lambda);
        if (lambda instanceof ToIntNullable) {
            return (ToIntNullable<T>) lambda;
        } else {
            return lambda::apply;
        }
    }
Returns a typed {@code ToIntNullable<T>} using the provided
{@code lambda}.

@param <T> type to extract from
@param lambda to convert
@return a typed {@code ToIntNullable<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/ToIntNullable.java