public static <T> Set<T> of(T value) {
        return Collections.singleton(value);
    }
Returns an unmodifiable set containing a single entry.

@param value the Set's value.
@param <T> the Set's value type.
@return a Set containing the specified value.
@throws NullPointerException if the value is {@code null}.
smithy-utils/src/main/java/software/amazon/smithy/utils/SetUtils.java