code: @UiThread
      public void collapseParent(@NonNull P parent) {
          ExpandableWrapper<P, C> parentWrapper = new ExpandableWrapper<>(parent);
          int flatParentPosition = mFlatItemList.indexOf(parentWrapper);
          if (flatParentPosition == INVALID_FLAT_POSITION) {
              return;
          }
  
          collapseViews(mFlatItemList.get(flatParentPosition), flatParentPosition);
      }
docs: Collapses the parent associated with a specified {@link P} in the list of parents.
  
  @param parent The {@code P} of the parent to collapse