code: public static List<CmsRelationType> filterWeak(Collection<CmsRelationType> relationTypes) {
  
          List<CmsRelationType> result = new ArrayList<CmsRelationType>(relationTypes);
          Iterator<CmsRelationType> it = result.iterator();
          while (it.hasNext()) {
              CmsRelationType type = it.next();
              if (type.isStrong()) {
                  it.remove();
              }
          }
          return result;
      }
docs: Returns all weak relation types in the given list.<p>
  
  @param relationTypes the collection of relation types to filter
  
  @return a list of {@link CmsRelationType} objects