partial class Examples
{
  public static Result InstanceDefinitionTree(RhinoDoc doc)
  {
    var instance_definitions = doc.InstanceDefinitions;
    var instance_definition_count = instance_definitions.Count;

    if (instance_definition_count == 0)
    {
      RhinoApp.WriteLine("Document contains no instance definitions.");
      return Result.Nothing;
    }

    var dump = new TextLog();
    dump.IndentSize = 4;

    for (int i = 0; i < instance_definition_count; i++)
      DumpInstanceDefinition(instance_definitions[i], ref dump, true);

    RhinoApp.WriteLine(dump.ToString());

    return Result.Success;
  }

  private static void DumpInstanceDefinition(InstanceDefinition instanceDefinition, ref TextLog dump, bool isRoot)
  {
    if (instanceDefinition != null && !instanceDefinition.IsDeleted)
    {
      string node = isRoot ? "─" : "└";
      dump.Print(string.Format("{0} Instance definition {1} = {2}\n", node, instanceDefinition.Index, instanceDefinition.Name));

      if (instanceDefinition.ObjectCount  > 0)
      {
        dump.PushIndent();
        for (int i = 0; i < instanceDefinition.ObjectCount ; i++)
        {
          var obj = instanceDefinition.Object(i);
          if (obj == null) continue;
          if (obj is InstanceObject)
            DumpInstanceDefinition((obj as InstanceObject).InstanceDefinition, ref dump, false); // Recursive...
          else
            dump.Print("\u2514 Object {0} = {1}\n", i, obj.ShortDescription(false));
        }
        dump.PopIndent();
      }
    }
  }
}

from scriptcontext import doc
import Rhino

def RunCommand():
    instanceDefinitions = doc.InstanceDefinitions
    instanceDefinitionCount = instanceDefinitions.Count

    if instanceDefinitionCount == 0:
        print("Document contains no instance definitions.")
        return

    dump = Rhino.FileIO.TextLog()
    dump.IndentSize = 4

    for i in range(0, instanceDefinitionCount):
        DumpInstanceDefinition(instanceDefinitions[i], dump, True)

    print(dump.ToString())

def DumpInstanceDefinition(instanceDefinition, dump, isRoot):
    if instanceDefinition != None and not instanceDefinition.IsDeleted:
        if isRoot:
            node = '-'
        else:
            node = '+'
        dump.Print(u"{0} Instance definition {1} = {2}\n".format(node, instanceDefinition.Index, instanceDefinition.Name))

        if instanceDefinition.ObjectCount  > 0:
            dump.PushIndent()
            for i in range(0, instanceDefinition.ObjectCount):
                obj = instanceDefinition.Object(i)
                if obj != None and type(obj) == Rhino.DocObjects.InstanceObject:
                    DumpInstanceDefinition(obj.InstanceDefinition, dump, False) # Recursive...
                else:
                    dump.Print(u"+ Object {0} = {1}\n".format(i, obj.ShortDescription(False)))
            dump.PopIndent()

if __name__ == "__main__":
    RunCommand()