std::pmr::memory_resource::memory_resource
From cppreference.com
                    
                                        
                    < cpp | memory | memory resource
                    
                                                            
                    | memory_resource() = default; | (1) | (since C++17) (implicitly declared) | 
| memory_resource(const memory_resource&) = default; | (2) | (since C++17) (implicitly declared) | 
1) Implicitly declared default constructor.
2) Implicitly declared copy constructor.


