Make MetaOperator registrable in Python.

include/aidge/operator/MetaOperator.hpp

@@ -28,7 +28,7 @@
 
 namespace Aidge {
 class MetaOperator_Op : public OperatorTensor,
-                public Registrable<MetaOperator_Op, std::array<std::string, 2>, std::function<std::unique_ptr<OperatorImpl>(const MetaOperator_Op &)>> {
+                public Registrable<MetaOperator_Op, std::array<std::string, 2>, std::function<std::shared_ptr<OperatorImpl>(const MetaOperator_Op &)>> {
 public:
     // outputs shared with micro-graph output Tensors
     // Micro-graph handling:

python_binding/operator/pybind_MetaOperatorDefs.cpp

@@ -194,12 +194,14 @@ void init_MetaOperatorDefs(py::module &m) {
 //   declare_PaddedMaxPoolingOp<3>(m);
   declare_LSTMOp(m);
 
-  py::class_<MetaOperator_Op, std::shared_ptr<MetaOperator_Op>, OperatorTensor>(m, "MetaOperator_Op", py::multiple_inheritance())
+  py::class_<MetaOperator_Op, std::shared_ptr<MetaOperator_Op>, OperatorTensor>(m, "MetaOperatorOp", py::multiple_inheritance())
   .def(py::init<const char *, const std::shared_ptr<GraphView>&>(),
           py::arg("type"),
           py::arg("graph"))
   .def("get_micro_graph", &MetaOperator_Op::getMicroGraph);
 
+  declare_registrable<MetaOperator_Op>(m, "MetaOperatorOp");
+
   m.def("meta_operator", &MetaOperator,
     py::arg("type"),
     py::arg("graph"),