graph
   {
   subgraph cluster01
   {
   n01[label="it,ct,ht"];
   n02[label="ft"];
   n03[label="gt"];
   n04[label="ot"];
   n01--n02;
   n01--n03;
   n01--n04;
   n01--m10;
   n01--m11;
   n01--m12;
   n02--m20;
   n02--m21;
   n02--m22;
   n03--m30;
   n03--m31;
   n03--m32;
   n04--m40;
   n04--m41;
   n04--m42;
   }
   }