    # File lib/active_support/core_ext/array/conversions.rb, line 57
            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