docs: public boolean canAcceptParent(Class<? extends ElementBase> clazz) {
          if (!canAcceptParent(getClass(), clazz)) {
              rejectReason = getDisplayName() + " does not accept " + clazz.getSimpleName() + " as a parent.";
          } else {
              rejectReason = null;
          }
          
          return rejectReason == null;
      }