docs: public final boolean isParentItem(int adapterPosition) {
          int itemCount = 0;
  
          int parentCount = parentItemCount();
          for (int i = 0; i < parentCount; i++) {
              if (itemCount == adapterPosition) {
                  return true;
              }
  
              itemCount += 1;
  
              if (isExpanded(i)) {
                  itemCount += childItemCount(i);
              } else {
                  // itemCount += 1;
              }
          }
  
          return false;
      }