code: public function setTransition($transition)
      {
          if ($transition instanceof SlideTransition) {
              $this->transition = $transition;
          } elseif (is_array($transition)) {
              $this->transition = new SlideTransition($transition);
          } else {
              $this->transition = null;
              trigger_error('Argument must be an object of class SlideTransition. Data loss!', E_USER_WARNING);
          }
  
          return $this;
      }
docs: Sets the "transition" of the SlideStructure.
  
  @param SlideTransition $transition
  
  @return SlideStructure