 version */ template< class Stepper , class System , class State , class Time , class Observer> Time integrate_n_steps(         Stepper stepper , System system , State &start_state ,         Time start_time , Time dt , size_t num_of_steps ,         Observer observer , stepper_tag ) {     typename odeint::unwrap_reference< Observer >::type &obs = observer;     typename odeint::unwrap_reference< Stepper >::type &st = stepper;      Time time = start_time;      for( size_t step = 0; step < num_of_steps ; ++step )     {         obs( start_state , time );         