如何在QTreeView小部件中更改图标

from PyQt5.QtCore import Qt, QModelIndex, QAbstractItemModel, QVariant
from PyQt5.QtGui import QIcon

class CustomModel(QAbstractItemModel):
    def __init__(self, data, parent=None):
        super(CustomModel, self).__init__(parent)
        self.rootItem = data

    def index(self, row, column, parent=QModelIndex()):
        if not self.hasIndex(row, column, parent):
            return QModelIndex()
        
        if not parent.isValid():
            parentItem = self.rootItem
        else:
            parentItem = parent.internalPointer()

        childItem = parentItem.child(row)
        if childItem:
            return self.createIndex(row, column, childItem)
        else:
            return QModelIndex()

    def parent(self, index):
        if not index.isValid():
            return QModelIndex()

        childItem = index.internalPointer()
        parentItem = childItem.parentItem()

        if parentItem == self.rootItem:
            return QModelIndex()

        return self.createIndex(parentItem.row(), 0, parentItem)

    def rowCount(self, parent=QModelIndex()):
        if parent.column() > 0:
            return 0

        if not parent.isValid():
            parentItem = self.rootItem
        else:
            parentItem = parent.internalPointer()

        return parentItem.childCount()

    def columnCount(self, parent=QModelIndex()):
        if parent.isValid():
            return parent.internalPointer().columnCount()
        else:
            return self.rootItem.columnCount()

    def data(self, index, role=Qt.DisplayRole):
        if not index.isValid():
            return QVariant()

        if role == Qt.DisplayRole or role == Qt.EditRole:
            item = index.internalPointer()
            return item.data(index.column())

        if role == Qt.DecorationRole:
            if index.column() == 0:
                item = index.internalPointer()
                icon = item.icon()
                if icon:
                    return QIcon(icon)
        
        return QVariant()

    def setData(self, index, value, role=Qt.EditRole):
        if role == Qt.EditRole:
            item = index.internalPointer()
            if index.column() == 0:
                item.setIcon(value)
            
            self.dataChanged.emit(index, index)
            return True
        
        return False

class TreeItem:
    def __init__(self, data, parent=None):
        self.parentItem = parent
        self.itemData = data
        self.childItems = []
        self.itemIcon = None

    def appendChild(self, item):
        self.childItems.append(item)

    def child(self, row):
        return self.childItems[row]

    def childCount(self):
        return len(self.childItems)

    def columnCount(self):
        return len(self.itemData)

    def data(self, column):
        if column < len(self.itemData):
            return self.itemData[column]

        return None

    def parentItem(self):
        return self.parentItem

    def row(self):
        if self.parentItem:
            return self.parentItem.childItems.index(self)

        return 0

    def icon(self):
        return self.itemIcon

    def setIcon(self, icon):
        self.itemIcon = icon

if __name__ == "__main__":
    import sys
    from PyQt5.QtWidgets import QApplication, QTreeView, QVBoxLayout, QWidget

    app = QApplication(sys.argv)
    window = QWidget()
    layout = QVBoxLayout(window)

    # 创建自定义模型
    rootItem = TreeItem(["Name", "Size"])
    childItem1 = TreeItem(["File1.txt", "10 KB"], rootItem)
    childItem2 = TreeItem(["File2.txt", "20 KB"], rootItem)
    rootItem.appendChild(childItem1)
    rootItem.appendChild(childItem2)
    model = CustomModel(rootItem)

    # 创建QTreeView小部件
    treeView = QTreeView()
    treeView.setModel(model)
    
    # 更改图标
    model.setData(model.index(0, 0), QIcon("folder.png"), Qt.EditRole)

    layout.addWidget(treeView)
    window.show()

    sys.exit(app.exec_())