code: func taskDefinitionResourceType(app *twelvefactor.Manifest) string {
  	check := []string{
  		"EMPIRE_X_TASK_DEFINITION_TYPE",
  		"ECS_TASK_DEFINITION", // For backwards compatibility.
  	}
  
  	for _, n := range check {
  		if v, ok := app.Env[n]; ok {
  			if v == "custom" {
  				return "Custom::ECSTaskDefinition"
  			}
  		}
  	}
  
  	// Default when not set.
  	return "AWS::ECS::TaskDefinition"
  }
docs: // Returns the name of the CloudFormation resource that should be used to create
  // custom task definitions.