efl/src/lib/elementary/elm_panel_part.eo

class Elm.Panel.Part (Efl.Object, Efl.Container)
{
   [[Elementary panel internal part class]]
   data: Elm_Part_Data;
   implements {
      Efl.Object.destructor;
      Efl.Container.content { get; set; }
      Efl.Container.content_unset;
   }
}