Cannot redeclare class YIKES_Custom_Product_Tabs_Display_Ext

I installed the plugin “Custom Product Tab” to add new tab in the tour list. and when I was adding the following code to the functions.php it gave me the error: Your PHP code changes were rolled back due to an error on line 22 of file wp-content/themes/travelwp/functions.php. Please fix and try saving again.

Cannot redeclare class YIKES_Custom_Product_Tabs_Display_Ext

Here is the code which i used from documentation:
if ( class_exists( ‘YIKES_Custom_Product_Tabs_Display’ ) ) {
class YIKES_Custom_Product_Tabs_Display_Ext extends YIKES_Custom_Product_Tabs_Display {
public function init() {
// Add our custom product tabs section to the tour page
add_filter( ‘tour_booking_default_product_tabs’, array( $this, ‘add_custom_product_tabs’ ) );
}
}
new YIKES_Custom_Product_Tabs_Display_Ext();
}

Please advice.

Regards,

Ravi