I created a user interface with qt designer. I created a function that will dynamically generate one widget on top of another. But the widget does not appear.

class MainWindow(QMainWindow):
    def __init__(self,parent=None,client=None):
        QMainWindow.__init__(self)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        self.showMaximized()
        ...

    def set_horizontal_layout(self,widget):
        return QHBoxLayout(widget)

    def add_new_widget(self):

        sizePolicy = QSizePolicy(QSizePolicy.Preferred, QSizePolicy.Expanding)

        sizePolicy1 = QSizePolicy(QSizePolicy.Expanding, QSizePolicy.Preferred)
        sizePolicy1.setHorizontalStretch(0)
        sizePolicy1.setVerticalStretch(0)

        frameArticle = QFrame(self.ui.widget_19) #from ui
        frameQte = QFrame(frameArticle)

        frameArticle.setObjectName(u"frameArticle")
        frameQte.setObjectName(u"frameQte")

        sizePolicy.setHeightForWidth(frameArticle.sizePolicy().hasHeightForWidth())
        frameArticle.setSizePolicy(sizePolicy)

        frameArticle.setFrameShape(QFrame.StyledPanel)
        frameArticle.setFrameShadow(QFrame.Raised)

        horizontalLayout1 = self.set_horizontal_layout(frameArticle)
        horizontalLayout1.setObjectName(u"horizontalLayout1")
        horizontalLayout2 = self.set_horizontal_layout(frameQte)
        horizontalLayout2.setObjectName(u"horizontalLayout2")

        sizePolicy1.setHeightForWidth(frameQte.sizePolicy().hasHeightForWidth())
        frameQte.setSizePolicy(sizePolicy1)
        frameQte.setMinimumSize(QSize(80, 0))
        frameQte.setMaximumSize(QSize(80, 16777215))
        frameQte.setFrameShape(QFrame.StyledPanel)
        frameQte.setFrameShadow(QFrame.Raised)

        spinQte = QSpinBox(frameQte)
        spinQte.setObjectName(u"spinQte")

        self.horizontalLayout1.addWidget(frameQte)
        self.horizontalLayout2.addWidget(spinQte)
    
    if __name__ == "__main__":
    app = QApplication(sys.argv)

    window = MainWindow()
    window.show()

    sys.exit(app.exec_())

Everything seems to be working fine but nothing appears on the interface