How to use Hooks?

CodeceptJS
1

Hello,
I am trying to use hooks(Custom Helpers | CodeceptJS). Except _init others hooks are not being called. I have declared all of them in the helper file.
Here is the code:

module.exports = function() {
return actor({
// Define custom steps here, use ‘this’ to access default methods of I.
// It is recommended to place a general ‘login’ function here.

  _afterSuite: function () {
    this.say("after suite!!");
    this.clearCookies();
  },

  _init:function(){
    this.say("init!!");
  },

  _after:function(){
    this.say("after");
  }

}

Please let me know on what I am missing out. Thanks in advance