AttributeError: 'PyQt5.QtCore.pyqtSignal' object has no attribute 'connect'

pyqt5信号要定义为类属性

#!/usr/bin/python3
# -*- coding: utf-8 -*-

from PyQt5.Qt import *
import sys

class Win(QWidget):
    my_singal = pyqtSignal(str)

    def __init__(self):
        super().__init__()
        self.initUI()
        self.setWindowTitle('Main Window')
        self.setGeometry(300, 300, 300, 150)

    def initUI(self):
        btn = QPushButton("Button",self)
        btn.move(50,50)
        self.my_singal.connect(self.mysignal)
        btn.clicked.connect(self.prn)

    def prn(self):
        print("Print Test")
        self.my_singal.emit("My Slot")

    def mysignal(self,para):
        print(para)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Win()
    ex.show()
    app.exec_()