Rewrote abs operator so it shares code

ops/abs/abs.go

@@ -0,0 +1,44 @@
+package abs
+
+import (
+	"github.com/advancedclimatesystems/gonnx/onnx"
+	"github.com/advancedclimatesystems/gonnx/ops"
+	"gorgonia.org/tensor"
+)
+
+var absTypeConstraint = [][]tensor.Dtype{
+	{tensor.Uint8, tensor.Uint16, tensor.Uint32, tensor.Uint64, tensor.Int8, tensor.Int16, tensor.Int32, tensor.Int64, tensor.Float32, tensor.Float64},
+}
+
+// Abs represents the ONNX abs operator.
+type Abs struct {
+	ops.BaseOperator
+}
+
+// newAbs creates a new abs operator.
+func newAbs(version int, typeConstraint [][]tensor.Dtype) *Abs {
+	return &Abs{
+		BaseOperator: ops.NewBaseOperator(
+			version,
+			1,
+			1,
+			typeConstraint,
+			"abs",
+		),
+	}
+}
+
+// Init initializes the abs operator.
+func (a *Abs) Init(*onnx.NodeProto) error {
+	return nil
+}
+
+// Apply applies the abs operator.
+func (a *Abs) Apply(inputs []tensor.Tensor) ([]tensor.Tensor, error) {
+	out, err := tensor.Abs(inputs[0])
+	if err != nil {
+		return nil, err
+	}
+
+	return []tensor.Tensor{out}, nil
+}