@SuppressWarnings("unchecked")
    static <T> Function<T, T> identity() {
        return (Function<T, T>) IDENTITY;
    }
Returns an identity function that always returns the given value.

@param <T> Type of value to return.
@return Returns the identity function.
smithy-utils/src/main/java/software/amazon/smithy/utils/FunctionalUtils.java