* Added serialization of old API map in ngraph. * Changed order type to int64_t. * Fixed uint64_t error, added comments. * Apply suggestions from code review Co-authored-by: Gleb Kazantaev <gleb.nnstu@gmail.com> * Added tests with undefined type and empty order. * Added set, get and has methods. * Fix in tests. * Apply suggestions from code review Co-authored-by: Ilya Churaev <ilyachur@gmail.com> * Made inline methods, changed to shared_ptr. * Small fix. * Moved methods to header file. * Small fix. Co-authored-by: Gleb Kazantaev <gleb.nnstu@gmail.com> Co-authored-by: Ilya Churaev <ilyachur@gmail.com>