...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Returns true
if the message
semantics indicate keep-alive.
bool keep_alive() const;
The value depends on the version in the message, which must be set to the final value before this function is called or else the return value is unreliable.