code: public void addRelationshipToTarget(final Level level, final RelationshipType type) {
          final TargetRelationship relationship = new TargetRelationship(this, level, type);
          levelRelationships.add(relationship);
          relationships.add(relationship);
      }
docs: Add a relationship to the target level.
  
  @param level The target level that is to be related to.
  @param type  The type of the relationship.