如何在QWidget中绘制一个简单的水平规则？

from PyQt5.QtWidgets import QWidget, QApplication
from PyQt5.QtGui import QPainter, QPen
from PyQt5.QtCore import Qt
import sys

class RuleWidget(QWidget):
    def paintEvent(self, event):
        painter = QPainter(self)
        pen = QPen(Qt.black, 1, Qt.SolidLine)
        painter.setPen(pen)
        painter.drawLine(0, self.height() / 2, self.width(), self.height() / 2)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = QWidget()
    layout = QVBoxLayout()
    
    rule_widget = RuleWidget()
    layout.addWidget(rule_widget)
    
    window.setLayout(layout)
    window.show()
    
    sys.exit(app.exec_())