docs: static Set<String> validatePlaysAndRelatesStructure(Casting casting) {
          Set<String> errors = new HashSet<>();
  
          //Gets here to make sure we traverse/read only once
          Thing thing = casting.getRolePlayer();
          Role role = casting.getRole();
          Relation relation = casting.getRelation();
  
          //Actual checks
          roleNotAllowedToBePlayed(role, thing).ifPresent(errors::add);
          roleNotLinkedToRelation(role, relation.type(), relation).ifPresent(errors::add);
  
          return errors;
      }