public static void AlterPartDefinition(this IContentDefinitionManager manager, string name, Action<ContentPartDefinitionBuilder> alteration)
 {
     var partDefinition = manager.GetPartDefinition(name) ?? new ContentPartDefinition(name);
     var builder = new ContentPartDefinitionBuilder(partDefinition);
     alteration(builder);
     manager.StorePartDefinition(builder.Build());
 }