You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: c3_charting.rb
    path of file: ./repos/manageiq/lib/manageiq/reporting/charting
    
    the code of the file until where you have to start completion: module ManageIQ
  module Reporting
    class C3Charting < ManageIQ::Reporting::Charting
      # for Charting.detect_available_plugin
      def self.available?
        true
      end

      # for Charting.detect_available_plugin
      def self.priority
        1000
      end

      # backend identifier
      def backend

    
      def sample_chart(options, _report_theme)
        sample = {
          :data => {
            :axis    => {},
            :tooltip => {},
            :columns => [
              ['data1', 30, 200, 100, 400, 150, 250],
              ['data2', 50, 20, 10, 40, 15, 25],
              ['data3', 10, 25, 10, 250, 10, 30]
            ],
          },
          :miqChart => options[:graph_type],
          :miq      => {:zoomed => false}
        }
        sample[:data][:groups] = [['data1', 'data2', 'data3']] if options[:graph_type].include?('Stacked')
        sample
      end