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: client.go
    path of file: ./repos/juju/api/common/secretsdrain
    
    the code of the file until where you have to start completion: // Copyright 2023 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.

package secretsdrain

import (
	"github.com/juju/errors"

	"github.com/juju/juju/api/base"
	apiwatcher "github.com/juju/juju/api/watcher"
	apiservererrors "github.com/juju/juju/apiserver/errors"
	coresecrets "github.com/juju/juju/core/secrets"
	"github.com/juju/juju/core/watcher"
	"github.com/juju/juju/rpc/params"
)

// Client is the api client for the SecretsDrain facade.
type Client struct {
	facade base.FacadeCaller
}

// NewClient creates a secrets api client.
func NewClient(facade base.FacadeCaller) *Client {
	return &Client{facade: facade}
}

func processListSecretResult(info params.ListSecretResult) (out coresecrets.SecretMetadata, _ error) {
	uri, err := coresecrets.ParseURI(info.URI)
	if err != nil {
		return out, errors
    
func (c *Client) ChangeSecretBackend(metaRevisions []ChangeSecretBackendArg) (ChangeSecretBackendResult, error) {
	var results params.ErrorResults
	out := ChangeSecretBackendResult{Results: make([]error, len(metaRevisions))}
	args := params.ChangeSecretBackendArgs{Args: make([]params.ChangeSecretBackendArg, len(metaRevisions))}
	for i, mdr := range metaRevisions {
		arg := params.ChangeSecretBackendArg{
			URI:      mdr.URI.String(),
			Revision: mdr.Revision,
			Content:  params.SecretContentParams{Data: mdr.Data},
		}
		if mdr.ValueRef != nil {
			arg.Content.ValueRef = &params.SecretValueRef{
				BackendID:  mdr.ValueRef.BackendID,
				RevisionID: mdr.ValueRef.RevisionID,
			}
		}
		args.Args[i] = arg
	}
	err := c.facade.FacadeCall("ChangeSecretBackend", args, &results)
	if err != nil {
		return out, errors.Trace(err)
	}
	if len(results.Results) != len(metaRevisions) {
		return out, errors.Errorf("expected %d result, got %d", len(metaRevisions), len(results.Results))
	}
	for i, result := range results.Results {
		out.Results[i] = apiservererrors.RestoreError(result.Error)
	}
	return out, nil
}