docs: public void modifyRelationship(Relationship relationship, String description, String technology) {
          if (relationship == null) {
              throw new IllegalArgumentException("A relationship must be specified.");
          }
  
          Relationship newRelationship = new Relationship(relationship.getSource(), relationship.getDestination(), description, technology, relationship.getInteractionStyle());
          if (!relationship.getSource().has(newRelationship)) {
              relationship.setDescription(description);
              relationship.setTechnology(technology);
          } else {
              throw new IllegalArgumentException("This relationship exists already: " + newRelationship);
          }
      }