Not able to get alert message on click of custom created button

1. I have created custom button called "SUBMIT" on module. (Working Fine)

2. I was trying to implement simple alert message on click of that button.

Process Followed:

https://support.sugarcrm.com/Documentation/Sugar_Developer/Sugar_Developer_Guide_10.3/Cookbook/Adding_Buttons_to_the_Record_View/#Adding_Buttons_without_Overriding_View_Controllers

 Extend and override the record view controller:

./custom/modules/Accounts/clients/base/views/record/record.js

Code:

({

extendsFrom: 'RecordView',

initialize: function (options) {
this._super('initialize', [options]);

//add listener for custom button
this.context.on('button:submit_button:click', this.submit_button, this);
},

submit_button: function() {

app.alert.show('submit-ok', {
level: 'success',
messages: 'Submitting Your Order .....',
autoClose: true
});

}
})

Please help with me with the correct  approach .