如何在uicollectionview中固定单元格的顺序

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    
    let data = ["Cell 1", "Cell 2", "Cell 3", "Cell 4", "Cell 5", "Cell 6"]
    let fixedIndexes = [0, 2, 4] // 固定单元格的索引
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let layout = UICollectionViewFlowLayout()
        let collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
        view.addSubview(collectionView)
    }
    
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return data.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = .lightGray
        cell.textLabel?.text = data[indexPath.item]
        
        if fixedIndexes.contains(indexPath.item) {
            // 固定单元格的样式
            cell.backgroundColor = .green
        }
        
        return cell
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: 100, height: 100)
    }
}