std::reference_wrapper::get, std::reference_wrapper::operator T&
From cppreference.com
                    
                                        
                    < cpp | utility | functional | reference wrapper
                    
                                                            
                    | operator T& () const; | (since C++11) | |
| T& get() const; | (since C++11) | |
Returns the stored reference.
Parameters
(none)
Return value
The stored reference.
Exceptions
1-2)noexcept specification:  
noexcept
  See also
| calls the stored function (public member function) |