code: func (c *CloudFormation) ListStackInstances(input *ListStackInstancesInput) (*ListStackInstancesOutput, error) {
  	req, out := c.ListStackInstancesRequest(input)
  	return out, req.Send()
  }
docs: // ListStackInstances API operation for AWS CloudFormation.
  //
  // Returns summary information about stack instances that are associated with
  // the specified stack set. You can filter for stack instances that are associated
  // with a specific AWS account name or region.
  //
  // Returns awserr.Error for service API and SDK errors. Use runtime type assertions
  // with awserr.Error's Code and Message methods to get detailed information about
  // the error.
  //
  // See the AWS API reference guide for AWS CloudFormation's
  // API operation ListStackInstances for usage and error information.
  //
  // Returned Error Codes:
  //   * ErrCodeStackSetNotFoundException "StackSetNotFoundException"
  //   The specified stack set doesn't exist.
  //
  // See also, https://docs.aws.amazon.com/goto/WebAPI/cloudformation-2010-05-15/ListStackInstances