I've linked another file to a pushButton in my main window. Every time I click it, the new window does open but the old (primary window) is still there. How do I close it or hide it without affecting the new window.

PS: I'm a newcomer here. Apologies for any idiocies or mistakes while posting this query on my part. Thank you!

Here's the relevant code:

```
    import sys  
    from PyQt5 import QtCore, QtGui, QtWidgets  
    from create2 import Ui_MainWindow  
    from PyQt5.QtWidgets import QMainWindow, QWidget  
    from PyQt5.QtCore import QMargins  

    class Ui_Form(object):  
        def setupUi(self, Form):  
            Form.setObjectName("Form")  
            Form.resize(813, 655)  
            self.widget = QtWidgets.QWidget(Form)  
            self.widget.setGeometry(QtCore.QRect(190, 50, 501, 591))  
            self.widget.setObjectName("widget")  
            .  
            .  
            .  
        def newusr_clk(self):  
            self.mainwin=QMainWindow()  
            self.ui=Ui_MainWindow()  
            self.ui.setupUi(self.mainwin)  
            self.mainwin.show() 

```