public function __construct(Ezer_ScopeInstance &$scope_instance, Ezer_ActivityStep $step)
 {
     parent::__construct($scope_instance, $step);
     $class = $step->getClass();
     if (!class_exists($class)) {
         throw new Ezer_StepClassNotFoundException($class);
     }
     if (!is_subclass_of($class, 'Ezer_Activity')) {
         throw new Ezer_StepClassNotActivityException($class);
     }
     $this->activity = new $class();
 }
 public function __construct(Ezer_ScopeInstance &$scope_instance, Ezer_AssignStep $step)
 {
     parent::__construct($scope_instance, $step);
 }
 public function __construct(Ezer_ScopeInstance &$scope_instance, Ezer_StepContainer $step_container)
 {
     parent::__construct($scope_instance, $step_container);
 }