# File lib/active_support/core_ext/array/conversions.rb, line 46
  def to_formatted_s(format = :default)
    case format
      when :db
        if respond_to?(:empty?) && self.empty?
          "null"
        else
          collect { |element| element.id }.join(",")
        end
      else
        to_default_s
    end
  end