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: subscriptions_helper.rb
    path of file: ./repos/ekylibre/app/helpers/backend
    
    the code of the file until where you have to start completion: module Backend
  # Helpers for subcriptions and subscription natures
  module SubscriptionsHelper
    # Shows subscriptions count and new subscriptions month by month over the last year
    def subscriptions_chart(nature, options = {})
      series = []

      options[
    
    def subscriptions_chart(nature, options = {})
      series = []

      options[:months] ||= 35
      stopped_on = options[:stopped_on] || Time.zone.today + 11.months
      started_on = options[:started_on] || stopped_on.beginning_of_month - options[:months].months

      categories = []
      date = started_on
      stopped_on = started_on + 1 if started_on >= stopped_on
      while date <= stopped_on
        categories << [date, date.end_of_month, date.l(format: '%b %Y')]
        date = date >> 1
      end