public function get_heading()
{
if ($this->object->has_status(array('completed', 'processing'))) {
return apply_filters('woocommerce_email_heading_customer_invoice_paid', $this->format_string($this->heading_paid), $this->object);
} else {
return apply_filters('woocommerce_email_heading_customer_invoice', $this->format_string($this->heading), $this->object);
}
}