std::experimental::reflect::Namespace
From cppreference.com
                    
                                        
                    < cpp | experimental | reflect
                    
                                                            
                    |   Defined in header  <experimental/reflect>
  | 
||
|   template< class T > concept Namespace = Scope<T> && /* see below */;  | 
(reflection TS) | |
The Namespace concept is satisfied if and only if T reflects a namespace including the global namespace (Note: Any such T that does not reflect the global namespace also satisfies ScopeMember).
Example
| This section is incomplete Reason: examples  | 
See also
| This section is incomplete Reason: templatization  |