code: public List<Relationship> getPreviousRelationships() {
          final List<Relationship> prevRelationships = new LinkedList<Relationship>();
          for (final Relationship r : relationships) {
              if (r.getType() == RelationshipType.PREVIOUS) {
                  prevRelationships.add(r);
              }
          }
          return prevRelationships;
      }
docs: Gets a list of previous relationships for the Topic.