graph {
  "1" [cluster="3", label="Node 1", pos="26.163,130.97"];
  "2" [cluster="3", label="Node 2", pos="270.82,243.14"];
  "3" [cluster="2", label="Node 3", pos="271.43,16.263"];
  "4" [cluster="2", label="Node 4", pos="670.15,16.263"];
  "5" [cluster="2", label="Node 5", pos="415.11,16.263"];
  "6" [cluster="1", label="Node 6", pos="513.44,131.26"];
  "1" -- "2";
  "2" -- "3";
  "1" -- "3";
  "4" -- "5";
  "4" -- "3";
  "3" -- "5";
  "6" -- "2";
  "6" -- "1";
  "6" -- "5";
}