code: def check_webhook_validation(app_configs=None, **kwargs):
  	
  	from . import settings as djstripe_settings
  
  	messages = []
  
  	validation_options = ("verify_signature", "retrieve_event")
  
  	if djstripe_settings.WEBHOOK_VALIDATION is None:
  		messages.append(
  			checks.Warning(
  				"Webhook validation is disabled, this is a security risk if the webhook view is enabled",
  				hint="Set DJSTRIPE_WEBHOOK_VALIDATION to one of {}".format(
  					", ".join(validation_options)
  				),
  				id="djstripe.W004",
  			)
  		)
  	elif djstripe_settings.WEBHOOK_VALIDATION == "verify_signature":
  		if not djstripe_settings.WEBHOOK_SECRET:
  			messages.append(
  				checks.Critical(
  					"DJSTRIPE_WEBHOOK_VALIDATION='verify_signature' but DJSTRIPE_WEBHOOK_SECRET is not set",
  					hint="Set DJSTRIPE_WEBHOOK_SECRET or set DJSTRIPE_WEBHOOK_VALIDATION='retrieve_event'",
  					id="djstripe.C006",
  				)
  			)
  	elif djstripe_settings.WEBHOOK_VALIDATION not in validation_options:
  		messages.append(
  			checks.Critical(
  				"DJSTRIPE_WEBHOOK_VALIDATION is invalid",
  				hint="Set DJSTRIPE_WEBHOOK_VALIDATION to one of {} or None".format(
  					", ".join(validation_options)
  				),
  				id="djstripe.C007",
  			)
  		)
  
  	return messages
docs: Check that DJSTRIPE_WEBHOOK_VALIDATION is valid