Feat: Support empty permutation vector for Transpose

Context

For Transpose Operator, ONNX allows passing an empty permutation vector.
In that case, Transpose operation reverses the dimensions of the input tensor.

Modified files

• Transpose.hpp, Transpose.cpp and pybind_Transpose.cpp, support empty permutation vector;
• Test_TransposeImpl.cpp, add Unit Test for empty permutation vector;

TODO

• Update Operator
• Add Unit Test

include/aidge/operator/Transpose.hpp

@@ -25,6 +25,11 @@
 #include "aidge/utils/Types.h"
 
 namespace Aidge {
+/**
+ * @brief implementation of the operator Transpose.
+ * @note Since this operator implementation is agnostic to the backend it is
+ * located here instead of in aidge_backend.
+ */
 class TransposeImpl : public OperatorImpl {
 public:
     TransposeImpl(const Operator& op, const std::string& backend = "")
@@ -33,8 +38,22 @@ public:
     void forward() override;
 };
 
-enum class TransposeAttr { OutputDimsOrder };
+enum class TransposeAttr {
+  /**
+   * @brief order of the ouput dims from the input dims. If left empty,
+   * the dimensions of input will be reversed.
+   */
+    OutputDimsOrder
+};
 
+/**
+ * @brief This operator has as purpose to transpose the axes of a given tensor.
+ * input#0 : Tensor to transpose
+ * @example Calling transpose() on a tensor of dimensions [1, 2, 3] with OutputDimsOrder=(1,0,2) result
+ * in a tensor of dim [2, 1, 3].
+ * @example Calling transpose() on a tensor of dimensions [1,2,3,4] with an empty OutputDimsOrder vector
+ * will result in a tensor of dim [4,3,2,1].
+ */
 class Transpose_Op : public OperatorTensor,
                 public Registrable<Transpose_Op, std::string, std::function<std::shared_ptr<OperatorImpl>(const Transpose_Op&)>> {
 
@@ -50,6 +69,10 @@ private:
 public:
     Transpose_Op() = delete;
 
+  /**
+   * @brief constructor for Transpose op
+   * @param[in] outputDimsOrder axes permutation order. By default axes are reversed.
+   */
     Transpose_Op(const std::vector<DimSize_t> &outputDimsOrder);
 
     /**
@@ -70,6 +93,9 @@ public:
     std::set<std::string> getAvailableBackends() const override;
 
     inline std::shared_ptr<Attributes> attributes() const override { return mAttributes; }
+    /**
+     * @brief axes new order, if left empty, axes will be reversed.
+     */
     inline std::vector<DimSize_t>& outputDimsOrder() const noexcept { return mAttributes -> getAttr<TransposeAttr::OutputDimsOrder>(); }
 
     static const std::vector<std::string> getInputsName(){
@@ -80,8 +106,8 @@ public:
     }
 };
 
-std::shared_ptr<Node> Transpose(const std::vector<DimSize_t> &outputDimsOrder,
-                                           const std::string& name = "");
+std::shared_ptr<Node> Transpose(const std::vector<DimSize_t> &outputDimsOrder = {},
+                                const std::string& name = "");
 }  // namespace Aidge
 
 namespace {