docs: public int getChildCount(Class<? extends ElementBase> clazz) {
          if (clazz == ElementBase.class) {
              return getChildCount();
          }
          
          int count = 0;
          
          for (ElementBase child : children) {
              if (clazz.isInstance(child)) {
                  count++;
              }
          }
          
          return count;
      }