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: recommendable.rb
    path of file: ./repos/simple_recommender/lib/simple_recommender
    
    the code of the file until where you have to start completion: module SimpleRecommender
  module Recommendable
    extend ActiveSupport::Concern
    DEFAULT_N_RESULTS = 10
    SIMILARITY_KEY = "similarity" # todo: allow renaming to avoid conflicts
    AssociationMetada
    
      def association_metadata(reflection)
        case reflection
        when ActiveRecord::Reflection::HasAndBelongsToManyReflection
          AssociationMetadata.new(
            reflection.join_table,
            reflection.foreign_key,
            reflection.association_foreign_key
          )
        when ActiveRecord::Reflection::ThroughReflection
          AssociationMetadata.new(
            reflection.through_reflection.table_name,
            reflection.through_reflection.foreign_key,
            reflection.association_foreign_key
          )
        else
          raise ArgumentError, "Association '#{reflection.name}' is not a supported type"
        end