try

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

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QToolButton
from PyQt5.QtGui import QIcon


class Example(QWidget):

    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.setGeometry(300, 300, 300, 220)
        self.show()


class PlusButton(QToolButton):

    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.icon = QIcon("plus.png"),
        self.popupMode = QtWidgets.QToolButton.InstantPopup
        self.menu()
        menu = QtWidgets.QMenu(button)
        menu.addAction(QtGui.QIcon("insert.png"), "Insert multiple rows")
        menu.addSeparator()
        menu.addAction("Place new rows above selected row")
        menu.addAction("Place new rows bellow selected row")
        menu.addAction("Place new rows at the end of the data view")
        button.setMenu(menu)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())