Print PDF View in Doctype List

frappe.listview_settings[‘Purchase Order’] = {
    button: {
    show: function(doc) {
    return true;
    },
    get_label: function() {
   return __(‘View’);  
   },
  get_description: function(doc) {
   return __(‘Open {0}’, [${doc.name}])
   },
   action: function(doc) {
   frappe.set_route("/app/print/Purchase Order/"+doc.name);
   }
  }
}