# File lib/dragonfly/active_model_extensions/attachment.rb, line 144
      def retained_attrs=(attrs)
        if changed? # if already set, ignore and destroy this retained content
          destroy_content(attrs[:uid])
        else
          attrs.each do |key, value|
            unless attribute_keys.include?(key)
              raise BadAssignmentKey, "trying to call #{attribute}_#{key} = #{value.inspect} via retained_#{attribute} but this is not allowed!"
            end
            model.send("#{attribute}_#{key}=", value)
          end
          sync_with_model
          set_job_from_uid
          self.retained = true
        end
      end