original_string: public function mark_major_change() {
          global $DB;
  
          // Clear old reset and completion notes.
          $DB->delete_records('user_preferences', ['name' => self::TOUR_LAST_COMPLETED_BY_USER . $this->get_id()]);
          $DB->delete_records('user_preferences', ['name' => self::TOUR_REQUESTED_BY_USER . $this->get_id()]);
          $this->set_config('majorupdatetime', time());
          $this->persist();
  
          return $this;
      }
code: public function mark_major_change() {
          global $DB;
  
          // Clear old reset and completion notes.
          $DB->delete_records('user_preferences', ['name' => self::TOUR_LAST_COMPLETED_BY_USER . $this->get_id()]);
          $DB->delete_records('user_preferences', ['name' => self::TOUR_REQUESTED_BY_USER . $this->get_id()]);
          $this->set_config('majorupdatetime', time());
          $this->persist();
  
          return $this;
      }
code_tokens: public function mark_major_change ( ) { global $ DB ; // Clear old reset and completion notes. $ DB -> delete_records ( 'user_preferences' , [ 'name' => self :: TOUR_LAST_COMPLETED_BY_USER . $ this -> get_id ( ) ] ) ; $ DB -> delete_records ( 'user_preferences' , [ 'name' => self :: TOUR_REQUESTED_BY_USER . $ this -> get_id ( ) ] ) ; $ this -> set_config ( 'majorupdatetime' , time ( ) ) ; $ this -> persist ( ) ; return $ this ; }
docstring: Update a tour giving it a new major update time.
  This will ensure that it is displayed to all users, even those who have already seen it.
  
  @return  $this
docstring_tokens: Update a tour giving it a new major update time . This will ensure that it is displayed to all users even those who have already seen it .