如何使用pyqt4将不同的背景颜色应用于树小部件中父文本的每一行

from PyQt4.QtGui import QStyledItemDelegate, QTreeView, QApplication, QStandardItemModel, QStandardItem, QColor, QPainter

class CustomDelegate(QStyledItemDelegate):
    def paint(self, painter, option, index):
        model = index.model()
        parent_index = index.parent()
        if parent_index.isValid():
            parent_item = model.itemFromIndex(parent_index)
            row = index.row()
            background_color = QColor(255, 255, 255)  # 默认背景颜色为白色
            if row % 2 == 0:
                background_color = QColor(200, 200, 200)  # 偶数行背景颜色为灰色
            painter.fillRect(option.rect, background_color)
        super().paint(painter, option, index)

# 创建一个QTreeView并设置自定义的QStyledItemDelegate
app = QApplication([])
tree_view = QTreeView()
model = QStandardItemModel()
tree_view.setModel(model)
delegate = CustomDelegate()
tree_view.setItemDelegate(delegate)

# 添加父文本和子文本到模型中
parent_item = QStandardItem("Parent Text")
model.appendRow(parent_item)
for i in range(5):
    child_item = QStandardItem("Child Text {}".format(i))
    parent_item.appendRow(child_item)

tree_view.show()
app.exec_()