message: Fixed a unit test with graph
  The string output now contains the layer info.
diff: @@ -279,11 +279,11 @@ TEST(GateTester, checkGenerateGraph) {
  std::string expected = R"expected(digraph G {
  node [shape=box style=filled]
  0 [label="bits=[0,1,2];id=0;name=InitialState"];
  -1 [label="bits=[1];id=1;name=H"];
  -2 [label="bits=[1,2];id=2;name=CNOT"];
  -3 [label="bits=[0,1];id=3;name=CNOT"];
  -4 [label="bits=[0];id=4;name=H"];
  -5 [label="bits=[2];id=5;name=Rz"];
  +1 [label="bits=[1];id=1;layer=0;name=H"];
  +2 [label="bits=[1,2];id=2;layer=1;name=CNOT"];
  +3 [label="bits=[0,1];id=3;layer=2;name=CNOT"];
  +4 [label="bits=[0];id=4;layer=3;name=H"];
  +5 [label="bits=[2];id=5;layer=3;name=Rz"];
  6 [label="bits=[0,1,2];id=6;name=FinalState"];
  0->1 ;
  0->2 ;
  