// reduced dimensions to the front. E.g. Given the equation "aabbcd->ca" we'd
  // first obtain the VJP for "bdca->ca", and then the VJP for "aabbcd->bdca".
  //
  // Obtain the input shape with reduced dimensions prepended, viz. [5,4,3,2].
  // This is the shape of the intermediate "bdca".
  Output output_grad_shape = Shape(scope, output_grad);
  auto grad_shape_with_reduced_labels =

    assertEqualCharNodes(traverser.breadthFirst(charactersOf("a")), "abcd");
    assertEqualCharNodes(traverser.breadthFirst(charactersOf("bd")), "bdca");
    assertEqualCharNodes(traverser.breadthFirst(charactersOf("dc")), "dcab");
    assertEqualCharNodes(traverser.breadthFirst(charactersOf("bc")), "bcda");
  }

  @Test
  public void forGraph_breadthFirst_twoCycles() {

    assertEqualCharNodes(traverser.breadthFirst(charactersOf("a")), "abcd");
    assertEqualCharNodes(traverser.breadthFirst(charactersOf("bd")), "bdca");
    assertEqualCharNodes(traverser.breadthFirst(charactersOf("dc")), "dcab");
    assertEqualCharNodes(traverser.breadthFirst(charactersOf("bc")), "bcda");
  }

  @Test
  public void forGraph_breadthFirst_twoCycles() {

		return "error: unknown instruction"
	}

	PC := pc
	// Special handling for some ops
	startArg := 0
	sep := " "
	opName := inst.Op.String()
	argList := inst.Args[:]

	switch opName {
	case "bc", "bcl", "bca", "bcla", "bclr", "bclrl", "bcctr", "bcctrl", "bctar", "bctarl":
		sfx := inst.Op.String()[2:]
		bo := int(inst.Args[0].(Imm))
		bi := inst.Args[1].(CondReg)
		atsfx := [4]string{"", "?", "-", "+"}

	assert(t, AXB, axb1, "axb1")
	axb2 := B.Union(A, alwaysNil)
	assert(t, AXB, axb2, "axb2")

	adb := A.Difference(B, alwaysNil)
	assert(t, ADB, adb, "adb")
	bda := B.Difference(A, nil)
	assert(t, BDA, bda, "bda")

	Ap1 := treePlus1([]int32{1, 2, 3, 4})

	ada1_1 := A.Difference(Ap1, smaller)
	assert(t, A, ada1_1, "ada1_1")
	ada1_2 := Ap1.Difference(A, smaller)
	assert(t, A, ada1_2, "ada1_2")

		}
		return op + " " + strings.Join(args, ", ")
	case BCCTRL:
		if int(inst.Args[0].(Imm))&20 == 20 { // unconditional
			return "BL (CTR)"
		}
		return op + " " + strings.Join(args, ",")
	case BCA, BCL, BCLA, BCLRL, BCTAR, BCTARL:
		return op + " " + strings.Join(args, ",")
	}
}

// plan9Arg formats arg (which is the argIndex's arg in inst) according to Plan 9 rules.
//