code: func (c *CloudFormation) UpdateStackSet(input *UpdateStackSetInput) (*UpdateStackSetOutput, error) {
  	req, out := c.UpdateStackSetRequest(input)
  	return out, req.Send()
  }
docs: // UpdateStackSet API operation for AWS CloudFormation.
  //
  // Updates the stack set, and associated stack instances in the specified accounts
  // and regions.
  //
  // Even if the stack set operation created by updating the stack set fails (completely
  // or partially, below or above a specified failure tolerance), the stack set
  // is updated with your changes. Subsequent CreateStackInstances calls on the
  // specified stack set use the updated stack set.
  //
  // 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 UpdateStackSet for usage and error information.
  //
  // Returned Error Codes:
  //   * ErrCodeStackSetNotFoundException "StackSetNotFoundException"
  //   The specified stack set doesn't exist.
  //
  //   * ErrCodeOperationInProgressException "OperationInProgressException"
  //   Another operation is currently in progress for this stack set. Only one operation
  //   can be performed for a stack set at a given time.
  //
  //   * ErrCodeOperationIdAlreadyExistsException "OperationIdAlreadyExistsException"
  //   The specified operation ID already exists.
  //
  //   * ErrCodeStaleRequestException "StaleRequestException"
  //   Another operation has been performed on this stack set since the specified
  //   operation was performed.
  //
  //   * ErrCodeInvalidOperationException "InvalidOperationException"
  //   The specified operation isn't valid.
  //
  //   * ErrCodeStackInstanceNotFoundException "StackInstanceNotFoundException"
  //   The specified stack instance doesn't exist.
  //
  // See also, https://docs.aws.amazon.com/goto/WebAPI/cloudformation-2010-05-15/UpdateStackSet