基于数值的PyQt表格视图背景颜色？

from PyQt5.QtCore import Qt, QAbstractTableModel
from PyQt5.QtGui import QColor, QBrush
from PyQt5.QtWidgets import QApplication, QTableView, QStyledItemDelegate

class TableModel(QAbstractTableModel):
    def __init__(self, data):
        super().__init__()
        self.data = data

    def rowCount(self, parent):
        return len(self.data)

    def columnCount(self, parent):
        return len(self.data[0])

    def data(self, index, role):
        if role == Qt.DisplayRole:
            return str(self.data[index.row()][index.column()])
        elif role == Qt.BackgroundRole:
            value = self.data[index.row()][index.column()]
            if value > 0:
                return QBrush(Qt.green)
            elif value < 0:
                return QBrush(Qt.red)
        return None

app = QApplication([])
table_view = QTableView()
data = [[1, 2, 3], [-1, -2, -3], [0, 0, 0]]
model = TableModel(data)
table_view.setModel(model)
table_view.setItemDelegate(QStyledItemDelegate())
table_view.show()
app.exec_()