You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: api_op_ApplyPendingMaintenanceAction.go
    path of file: ./repos/aws-sdk-go-v2/service/docdb
    
    the code of the file until where you have to start completion: // Code generated by smithy-go-codegen DO NOT EDIT.

package docdb

import (
	"context"
	"fmt"
	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
	"github.com/aws/aws-sdk-go-v2/service/docdb/types"
	"github.com/aws/smithy-go/middleware"
	smithyhttp "github.com/aws/smithy-go/transport/http"
)

// Applies a pending maintenance action to a resource (for example, to an Amazon
// DocumentDB instance).
func (c *Client) ApplyPendingMaintenanceAction(ctx context.Context, params *ApplyPendingMaintenanceActionInput, optFns ...func(*Options)) (*ApplyPendingMaintenanceActionOutput, error) {
	if params == nil {
		params = &ApplyPendingMaintenanceActionInput{}
	}

	result, metadata, err := c.invokeOperation(ctx, "ApplyPendingMaintenanceAction", params, optFns, c.addOperationApplyPendingMaintenanceActionMiddlewares)
	if err != nil {
		return nil, err
	}

	out := result.(*ApplyPendingMaintenanceActionOutput)
	out.ResultMetadata = metadata
	return out, nil
}

// Represents the input to ApplyPendingMaintenanceAction .
type ApplyPendingMaintenanceActionInput struct {

	// The pending maintenance action to apply to this resource. Valid values:
	// system-update , db-upgrade
	//
	// This member is required.
	ApplyAction *string

	// A value that specifies the type of opt-in request or undoes an opt-in request.
	// An opt-in request of type immediate can't be undone. Valid values:
	//   - immediate - Apply the maintenance action immediately.
	//   - next-maintenance - Apply the maintenance action during the next maintenance
	//   window for the resource.
	//   - undo-opt-in - Cancel any existing next-maintenance opt-in requests.
	//
	// This member is required.
	OptInType *string

	// The Amazon Resource Name (ARN) of the resource that the pending maintenance
	// action applies to.
	//
	// This member is required.
	ResourceIdentifier *string

	noSmithyDocumentSerde
}

type ApplyPendingMaintenanceActionOutput struct 
    
func (c *Client) addOperationApplyPendingMaintenanceActionMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsAwsquery_serializeOpApplyPendingMaintenanceAction{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsAwsquery_deserializeOpApplyPendingMaintenanceAction{}, middleware.After)
	if err != nil {
		return err
	}
	if err := addProtocolFinalizerMiddlewares(stack, options, "ApplyPendingMaintenanceAction"); err != nil {
		return fmt.Errorf("add protocol finalizers: %v", err)
	}

	if err = addlegacyEndpointContextSetter(stack, options); err != nil {
		return err
	}
	if err = addSetLoggerMiddleware(stack, options); err != nil {
		return err
	}
	if err = addClientRequestID(stack); err != nil {
		return err
	}
	if err = addComputeContentLength(stack); err != nil {
		return err
	}
	if err = addResolveEndpointMiddleware(stack, options); err != nil {
		return err
	}
	if err = addComputePayloadSHA256(stack); err != nil {
		return err
	}
	if err = addRetry(stack, options); err != nil {
		return err
	}
	if err = addRawResponseToMetadata(stack); err != nil {
		return err
	}
	if err = addRecordResponseTiming(stack); err != nil {
		return err
	}
	if err = addClientUserAgent(stack, options); err != nil {
		return err
	}
	if err = smithyhttp.AddErrorCloseResponseBodyMiddleware(stack); err != nil {
		return err
	}
	if err = smithyhttp.AddCloseResponseBodyMiddleware(stack); err != nil {
		return err
	}
	if err = addSetLegacyContextSigningOptionsMiddleware(stack); err != nil {
		return err
	}
	if err = addOpApplyPendingMaintenanceActionValidationMiddleware(stack); err != nil {
		return err
	}
	if err = stack.Initialize.Add(newServiceMetadataMiddleware_opApplyPendingMaintenanceAction(options.Region), middleware.Before); err != nil {
		return err
	}
	if err = addRecursionDetection(stack); err != nil {
		return err
	}
	if err = addRequestIDRetrieverMiddleware(stack); err != nil {
		return err
	}
	if err = addResponseErrorMiddleware(stack); err != nil {
		return err
	}
	if err = addRequestResponseLogging(stack, options); err != nil {
		return err
	}
	if err = addDisableHTTPSMiddleware(stack, options); err != nil {
		return err
	}
	return nil
}