Rendering a Chart with a Netzke component

my_chart.js

{

    initComponent: function(params)
    {
        // Define the model
        Ext.define(this.id, {
          extend: 'Ext.data.Model',
          idProperty: this.pri, // Primary key
          fields: [{
                    name: 'month',
                    type: 'int'
                    },
                    {
                    name: 'comission',
                    type: 'float'
                    }]
        });
 
       var store = new Ext.data.Store({
                            model: this.id,
                            proxy: {
                                type: 'direct',
                                directFn: Netzke.providers[this.id].get_data,
                                reader: {
                                    type: 'json',
                                    root: 'sales'
                                }
                            },
                            autoLoad: true
        });
        this.store = store;
        
        Netzke.classes.MyChart.superclass.initComponent.call(this);
    }
}

my_chart.rb

  class MyChart < Netzke::Base
    # Our JS class will be inherited from Ext.chart.Chart
    js_base_class "Ext.chart.Chart"


    js_mixin :my_chart
    include Netzke::Basepack::DataAccessor

    js_properties :title => 'Simple Chart', :width => 800, :height => 600
    
    def js_config #:nodoc:
      super.merge({
        :animate => true,
         :model => config[:model],
         :pri => data_class.primary_key,
        :axes => [{
                    :type => 'Numeric',
                    :position => 'left',
                    :fields => ['comission'],
                    :title => 'Sample Values',
                    :grid => true,
                    :minimum => 0
                }, {
                    :type => 'Category',
                    :position => 'bottom',
                    :fields => ['month'],
                    :title => 'Sample Metrics'
                }],

                 :series => [{
                     :type => 'column',
                     :axis => 'left',
                     :gutter => 80,
                     :stacked => true,
                    :xField => 'month',
                    :yField => 'comission'
                 }]

     })
    end


  endpoint :get_data do |params|
    sales = data_class.all()
    sales.map do |s|
      {:month => s.month, :comission => s.comission}
    end
  end
end