[bug] ComputeGraph dfs and bfs graph traverse bug

[cycheng]

Test Case:

onnc::Module module; IRBuilder builder(module); ComputeGraph& cg = *builder.CreateComputeGraph("top-level");

ComputeOperator op1 = builder.AddComputeOp(); ComputeOperator op2 = builder.AddComputeOp(); ComputeOperator op3 = builder.AddComputeOp(); ComputeOperator op4 = builder.AddComputeOp();

// op1 op2 // \ /
// op3 // | // op4 cg.addOperand(op1, op3); cg.addOperand(op2, op3); cg.addOperand(op3, op4);

Expect dfs traversing output: op1 op3 op4 op2 Actual output: op1

[lubatang]

Got it. I'll write a unittest and resolve it.