on click button, there appears a new qlineedit at the end of the window but it should appear at the center between other widgets-PYQT5

This snippet of code has two labels and two buttons one is ok and one is cancel. when i click ok there appears a new field qLine edit at the top but i wanted to make appear that qlineedit in the center betwen two labels.

'''

class Example(QWidget):

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

    self.initUI()

def initUI(self):

    self.label_1 = QLabel('Normal Label', self)
    self.label_2 = QLabel('second label', self)
    self.okButton = QPushButton("OK")
    self.okButton.clicked.connect(self.on_click_additional_field)
    self.cancelButton = QPushButton("Cancel")

    self.hbox = QVBoxLayout()
    self.hbox.addStretch(1) 
    self.hbox.addWidget(self.label_1)
    self.hbox.addWidget(self.label_2)
    self.hbox.addWidget(self.okButton)
    self.hbox.addWidget(self.cancelButton)

    self.vbox = QVBoxLayout()
    self.vbox.addStretch(1)
    self.vbox.addLayout(self.hbox)

    self.setLayout(self.vbox)
    self.setWindowTitle('Buttons')
    self.show()

def on_click_additional_field(self):

        self.inspection_dir_path_txt_box = QLineEdit(self)
        # self.inspection_dir_path_txt_box.installEventFilter(self)
        self.inspection_dir_path_txt_box.move(100, 20)
        self.x1 = len(self.vbox)-1
        self.vbox.insertWidget(len(self.vbox)-2,self.inspection_dir_path_txt_box)

    # self.setGeometry(300, 300, 300, 150)

'''