Update order status to `processing` for the cheque payments method

functions.php

add_action('woocommerce_order_status_changed', 'wc_auto_complete_by_payment_method');

function wc_auto_complete_by_payment_method($order_id)
{

if ( ! $order_id ) {        
return;
}

global $product;
$order = wc_get_order( $order_id );  // Get the order ID.

/* Checks if the order is on hold. If it is on hold, and if the payment method is cheque payments, set the order status to `Processing` */

if ($order->data['status'] == 'on-hold') {        
$payment_method=$order->get_payment_method();
if ($payment_method == "cheque")
{
$order->update_status( 'processing' );
}

}

}