# File lib/new_relic/agent/javascript_instrumentor.rb, line 176
      def append_custom_attributes!(txn, atts)
        custom_attributes = txn.attributes.custom_attributes_for(NewRelic::Agent::AttributeFilter::DST_BROWSER_MONITORING)
        unless custom_attributes.empty?
          atts[ATTS_USER_SUBKEY] = custom_attributes
        end
      end