digraph G {

subgraph cluster_1 {
  label = "taskflow1";
  A1->B1;
  A1->C1;
  B1->D1;
  C1->D1;
}
  
subgraph cluster_2 {
  label = "taskflow2";
  A2->B2->C2->D2;
}
  
subgraph cluster_3 {
  label = "taskflow3";
  A3->B3;
  A3->C3;
  A3->D3;
}
}