Bring to the front the MainWindow in Pyqt5

I am dealing with the following problem, while I am having multiple windows open, i would like to build a function linked to a button to bring to the front the Main window.

Thank you in advance.

import sys
from PyQt5 import QtGui
from PyQt5.QtWidgets import (QApplication, QMainWindow, QPushButton, 
                              QLabel)

class Window2(QMainWindow):                           # <===
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Window 2")
        self.pushButton = QPushButton("Back to window1", self)
        self.pushButton.clicked.connect(self.window1) 


    def window1(self):                                             # <===
        pass;


class Window(QMainWindow):
    def __init__(self):
        super().__init__()

        self.title = "First Window"
        self.top = 100
        self.left = 100
        self.width = 680
        self.height = 500

        self.pushButton = QPushButton("Go to window 2 ", self)
        self.pushButton.move(275, 200)
            
        self.label = QLabel("window 1", self)
        self.label.move(285, 175)
        self.setWindowTitle(self.title)
        self.setGeometry(self.top, self.left, self.width, self.height)

        self.pushButton.clicked.connect(self.window2)              # <===



    def window2(self):                                             # <===
        self.w = Window2()
        self.w.show()
        
        


def main(): 
    
    app = QApplication(sys.argv)
    window =  Window()

    window.show()
    #app.exec_()
    exit(app.exec_())

if __name__=='__main__':
    main()

Regards

I am expecting a function to call back the widget "Window"

You could emit a signal from your second window that your fist window listens for, and calls .raise_() when triggered.

Update: Added a call to activateWindow in the first windows callback. thanks @musicmante

For example:

import sys
from PyQt5 import QtGui
from PyQt5.QtCore import pyqtSignal  # import signal
from PyQt5.QtWidgets import (QApplication, QMainWindow, QPushButton,
                              QLabel)

class Window2(QMainWindow):

    unfocus = pyqtSignal()   # create signal

    def __init__(self, parent=None):
        super().__init__(parent=parent)
        self.setWindowTitle("Window 2")
        self.pushButton = QPushButton("Back to window1", self)
        # button press emits signal
        self.pushButton.clicked.connect(self.unfocus.emit) 


class Window(QMainWindow):
    def __init__(self):
        super().__init__()
        self.title = "First Window"
        self.top = 100
        self.left = 100
        self.width = 680
        self.height = 500
        self.pushButton = QPushButton("Go to window 2 ", self)
        self.pushButton.move(275, 200)
        self.label = QLabel("window 1", self)
        self.label.move(285, 175)
        self.setWindowTitle(self.title)
        self.setGeometry(self.top, self.left, self.width, self.height)
        self.pushButton.clicked.connect(self.window2)              # <===

    def window2(self):                                             # <===
        self.w = Window2()
        self.w.unfocus.connect(self.bring_to_top)  # listen for signal and raise_ to top focus
        self.w.show()

    def bring_to_top(self):
        self.activateWindow()
        self.raise_()

def main():
    app = QApplication(sys.argv)
    window =  Window()
    window.show()
    #app.exec_()
    exit(app.exec_())

if __name__=='__main__':
    main()