extractSingle/extractArray in seralizers/application.js not getting called

I have an Ember/EmberData (version 2.1.0) application that is to display a list of posts (created from a json payload) on the home page, with the route

this.route("posts", { path: "/" });

However, the posts retrieved from the server are not in the format expected by EmberData i.e. they do not have a top level namespace. Therefore, I created a file

serializers/application.js

and included an extractSingle and an extractArray function in it, but neither of them are getting called, and the error message is therefore not goig away

Error while processing route: posts Assertion Failed: You must include an 'id' for undefined in an object passed to 'push

This error was preceeded by a warning:

`WARNING: "Encountered "0" [and "1"] in payload, but no model was found for model name "0" (resolved model name using em@serializer:posts.modelNameFRomPayloadKey("0")

I also created a file

 serializers/posts.js 

and included the same functions there, as well (extending the ApplicationAdapter) but neither of them are getting called also

Code from /serializers/application.js

import DS from 'ember-data'

export default DS.RESTSerializer.extend({
      extractSingle: function(store, type, payload, id){
          var convertedPayload = {};
          convertedPayload[type.modelName] = payload;
          convertedPayload.id = id;
          return this._super(store, type, convertedPayload, id}
      },
      extractArray: function(store, type, payload){
         var convertedPayload = {};
         convertedPayload[type.modelName = payload;
         return this._super(store, type, convertedPayload);
      },
      serializeIntoHash: function(hash, type, record, options){
         //ommitted
      }
}