Fix softmax binding (wrong argument type)

python_binding/operator/pybind_Softmax.cpp

@@ -21,7 +21,7 @@ namespace Aidge {
 
 void init_Softmax(py::module& m) {
     py::class_<Softmax_Op, std::shared_ptr<Softmax_Op>, OperatorTensor>(m, "SoftmaxOp", py::multiple_inheritance())
-        .def(py::init<std::size_t>(), py::arg("axis"))
+        .def(py::init<std::int32_t>(), py::arg("axis"))
         .def_static("get_inputs_name", &Softmax_Op::getInputsName)
         .def_static("get_outputs_name", &Softmax_Op::getOutputsName);
     declare_registrable<Softmax_Op>(m, "SoftmaxOp");