code: @NullSafe
    public static <T> Set<T> nullSafeSet(Set<T> set) {
      return set != null ? set : Collections.emptySet();
    }
docs: Null-safe method returning the given {@link Set} or an empty {@link Set} if null.
  
  @param <T> Class type of the elements in the {@link Set}.
  @param set {@link Set} to evaluate.
  @return the given {@link Set} or an empty {@link Set} if null.
  @see java.util.Collections#emptySet()
  @see java.util.Set