code: public Set<String> setToString(final Set<?> target) {
          if (target == null) {
              return null;
          }
          final Set<String> result = new LinkedHashSet<String>(target.size() + 2);
          for (final Object element : target) {
              result.add(toString(element));
          }
          return result;
      }
docs: <p>
  Performs a null-safe {@code toString()} operation on each
  element of the set.
  </p>
  
  @param target the set of objects on which toString will be executed
  @return for each element: the result of calling {@code target.toString()}
  if target is not null, {@code null} if target is null.
  @since 2.0.12