public override ListViewHolder OnCreateGroupViewHolder(ViewGroup parent, int viewType)
 {
     LayoutInflater inflater = LayoutInflater.From(parent.Context);
     View itemView = inflater.Inflate(Resource.Layout.example_list_view_group_header, parent, false);
     GroupItemViewHolder customHolder = new GroupItemViewHolder(itemView);
     return customHolder;
 }