code: private int getPackedGroupPosition(final int groupIndex) {
          int packedPosition = getHeaderViewsCount();
  
          if (groupIndex > 0) {
              for (int i = groupIndex - 1; i >= 0; i--) {
                  packedPosition += getExpandableListAdapter().getChildrenCount(i) + 1;
              }
          }
  
          return packedPosition;
      }
docs: Returns the packed position of a group, which corresponds to a specific index.
  
  @param groupIndex
  The index of the group, whose packed position should be returned, as an {@link
  Integer} value
  @return The packed position of the group, which corresponds to the given index, as an {@link
  Integer} value