Custom Slack Renderer

I’ve implemented a custom slack renderer and I’ve placed this file in the great_expectation/plugins directory and configured it the checkpoint action_list as follows. But during runtime it’s unable to locate the custom renderer. Please let me know if I’m missing something here. Thanks.

 - name: send_slack_notification_on_validation_result
      class_name: SlackNotificationAction
      slack_webhook: ${SLACK_WEBHOOK}
      notify_on: failure
        - local_site
        module_name: great_expectations.plugins.slack_custom_renderer
        class_name: SlackCustomRenderer