QGraphicsItem调用update不生效

from PySide6 import QtCore,QtWidgets,QtGui

class UiScene(QtWidgets.QGraphicsScene):
    u'画图'

    def __init__(self,parent=None):
        super().__init__(parent)
        self.setStickyFocus(True)

        self.currentItem = None

    def mousePressEvent(self, event: QtWidgets.QGraphicsSceneMouseEvent) -> None:
        print("mouse press")
        pos = event.scenePos()
        self.currentItem = self.addLine(QtCore.QLine(pos.x(),pos.y(),1,1),QtGui.QPen(QtCore.Qt.red))        
        return super().mousePressEvent(event)

    def mouseReleaseEvent(self, event: QtWidgets.QGraphicsSceneMouseEvent) -> None:
        return super().mouseReleaseEvent(event)

    def mouseMoveEvent(self, event: QtWidgets.QGraphicsSceneMouseEvent) -> None:
        pos = event.scenePos()
        if self.currentItem:
            line = self.currentItem.line()
            line.setP2(event.pos())
            self.currentItem.setLine(line)
            self.currentItem.update()
            self.update()
        return super().mouseMoveEvent(event)