{
       "_id": "fTvDyoPyewBgZ66Ge",
       "name": "Testgruppe1",
       "type": "group",
       "children": [
          {
             // IMPORTANT: "_id" is missing for the user!
             "name": "100 Tage Sommer",
             "type": "user",
             "children": [
               {
                  "_id": "T5itqnm84ZzTM54Zp",
                  "name": "100 Liste 1",
                  "type": "list"
               },
               {
                  "_id": "BCJKCZXhjibY7Qdyw",
                 "name": "100 Liste 2",
                  "type": "list"
               }
            ]
         },
         {
            "name": "Amoni",
            "type": "user",
            // this "children" could acutally be omitted as this user does not have any lists ... but I don't know how! Not that important though ...
            "children": [
               {
                  "type": "list"
               }
            ]
         }
      ]
   }