show extra fields in dokan invoices

As per your instruction in this link
https://docs.wedevs.com/how-to-create-extra-fields-in-store-settings-page/

We created 4 fields in store settings for sellers.

I want to display Text field1 in invoice.

Here is my code:

/**
     * Filter Text field1
     * 
     * @since 1.1
     * 
     * @global type $wpo_wcpdf
     * 
     * @param type $billing_city
     * 
     * @return string $billing_city
     */
    function wpo_wcpdf_add_dokan_billing_city( $billing_city ) {

        global $wpo_wcpdf;
        // If parent order keep Original Store name else set seller store name
        if ( $wpo_wcpdf->export->order->post->post_parent == 0 ) {

            if ( function_exists( 'dokan_get_seller_ids_by' ) ) {

                $seller_list = dokan_get_seller_ids_by( $wpo_wcpdf->export->order->id );

            } else {

                $seller_list = array_unique( array_keys( dokan_get_sellers_by( $wpo_wcpdf->export->order->id ) ) );

            }

            if ( count( $seller_list ) > 1 ) {

                return $billing_city;

            } else {

                $seller_id  = $seller_list[0];

                $store_info = dokan_get_store_info( $seller_id );

                $billing_city = !empty( $store_info['billing_city'] ) ? $store_info['billing_city'] : __( 'store_info', 'dokan-invoice' );

                return $billing_city . '<br /><br />Company Name: ' . $billing_city;
            }

        } else {

            $seller_id  = $wpo_wcpdf->export->order->post->post_author;
            
            $store_info = dokan_get_store_info( $seller_id );

            $billing_city = !empty( $store_info['billing_city'] ) ? $store_info['billing_city'] : __( 'store_info', 'dokan-invoice' );

            return $billing_city . '<br /><br />Text field1: ' . $billing_city;
        }
    }

I have also added action in dokan-invoice.php

add_filter( 'wpo_wcpdf_billing_city', array( $this,'wpo_wcpdf_add_dokan_billing_city'), 10, 1 );

But,I am unable to get the Text field1 value which is saved in store settings page.I can easily view the field data from seller panel.But,it is not coming in my invoice.