class ActiveRecord::Associations::Builder::HasAndBelongsToMany

def middle_reflection(join_model)
  middle_name = [lhs_model.name.downcase.pluralize,
                 association_name.to_s].sort.join("_").gsub("::", "_").to_sym
  middle_options = middle_options join_model
  HasMany.create_reflection(lhs_model,
                            middle_name,
                            nil,
                            middle_options)
end