Add __setattr__ and __getattr__ methods for Attributes. This recquired a change in the order of derived class declaration, see https://github.com/pybind/pybind11/issues/3804

Add a trampoline to Node.add_child in order to set None default value to avoid conversion of nullptr -> std::shared_ptr.

Fix numpy -> tensor with latest tensorImpl changes (copyFromHost instead of setRawPtr) + Use of std::int32_t instead of in and std::int64_t instead of long to fit Data.hpp convention.