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: key_value.rb
    path of file: ./repos/brew/Library/Homebrew/vendor/bundle-standalone/ruby/2.3.0/gems/i18n-1.5.3/lib/i18n/backend
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

require 'i18n/backend/base'

module I18n

  begin
    require 'oj'
    class JSON
      class << self
        def encode(value)
          Oj::Rails.encode(value)
        end
        def decode(value)
          Oj.load(value)
        end
      end
    end
  rescue LoadError
    require 'active_support/json'
    JSON = ActiveSupport::JSON
  end

  module Backend
    # This is a basic backend for key value stores. It receives on
    # initialization the store, which should respond to three methods:
    #
    # * store#[](key)         - Used to get a value
    # * store#[]=(key, value) - Used to set a value
    # * store#keys            - Used to get all keys
    #
    # Since these stores only supports string, all values are converted
    # to JSON before being stored, allowing it to also store booleans,
    # hashes and arrays. However, this store does not support Procs.
    #
    # As the ActiveRecord backend, Symbols are ju
    
        def translations
          @translations = @store.keys.clone.map do |main_key|
            main_value = JSON.decode(@store[main_key])
            main_key.to_s.split(".").reverse.inject(main_value) do |value, key|
              {key.to_sym => value}
            end
          end.inject{|hash, elem| hash.deep_merge!(elem)}.deep_symbolize_keys
        end

        def init_translations
          # NO OP
          # This call made also inside Simple Backend and accessed by
          # other plugins like I18n-js and babilu and
          # to use it along with the Chain backend we need to
          # provide a uniform API even for protected methods :S
        end

        def subtrees?
          @subtrees
        end

        def lookup(locale, key, scope = [], options = EMPTY_HASH)
          key   = normalize_flat_keys(locale, key, scope, options[:separator])
          value = @store["#{locale}.#{key}"]
          value = JSON.decode(value) if value

          if value.is_a?(Hash)
            value.deep_symbolize_keys
          elsif !value.nil?
            value
          elsif !@subtrees
            SubtreeProxy.new("#{locale}.#{key}", @store)
          end
        end