我试图连接来自已创建对象的信号，但出现错误。这是我的代码的简化版本：

class OverviewWindow(QMainWindow):
    def __init__(self, projectClusters, users, contributorDict, userLastRevPerProj):
        QMainWindow.__init__(self)
        # Code....

    def createUserNodes(self):
        userNodes = {}
        nodeSpread = 50
        yPos = -400
        nodeSpan = nodeSpread + 100
        width = (len(self.usersFilt) - 1) * nodeSpan
        xPos = 0 - (width / 2)

        for user in self.usersFilt:
            newItem = NodeItem(xPos, yPos, self.nodeDiameter, user, True)
            newItem.nodeDoubleClicked.connect(self.dc)
            userNodes[user] = newItem
            self.graphicsScene.addItem(newItem)
            xPos += nodeSpan

        return userNodes

    @pyqtSlot(str)
    def dc(self, text):
        print(text)


class NodeItem(QGraphicsItem):
    nodeDoubleClicked = pyqtSignal(str)

    def __init__(self, xPos, yPos, diameter, text, isUserNode):
        super(NodeItem, self).__init__()
        # Code...

    def mouseDoubleClickEvent(self, event):
        self.nodeDoubleClicked.emit(self.texts)

尝试运行它时，出现以下错误消息：

line 84, in createUserNodes
newItem.nodeDoubleClicked[str].connect(self.dc)
TypeError: NodeItem cannot be converted to PyQt5.QtCore.QObject in this context

我不知道这意味着什么或如何解决。