How to use the harvesters._private.frontend.pyqt5.device_list.ComboBox function in harvesters

observers.append(button_dev_attribute)

        #
        self._widget_about = About(self)
        button_about = ActionShowAbout(
            icon='about.png', title='About', parent=self,
            action=self.action_on_show_about
        )
        button_about.setToolTip(
            compose_tooltip('Show information about Harvester')
        )
        button_about.toggle()
        observers.append(button_about)

        #
        self._widget_device_list = ComboBox(self)
        self._widget_device_list.setSizeAdjustPolicy(
            QComboBox.AdjustToContents
        )
        shortcut_key = 'Ctrl+Shift+d'
        shortcut = QShortcut(QKeySequence(shortcut_key), self)

        def show_popup():
            self._widget_device_list.showPopup()

        shortcut.activated.connect(show_popup)
        self._widget_device_list.setToolTip(
            compose_tooltip('Select a device to connect', shortcut_key)
        )
        observers.append(self._widget_device_list)
        for d in self.harvester_core.device_info_list:
            self._widget_device_list.addItem(d)

observers.append(button_dev_attribute)

        #
        self._widget_about = About(self)
        button_about = ActionShowAbout(
            icon='about.png', title='About', parent=self,
            action=self.action_on_show_about
        )
        button_about.setToolTip(
            compose_tooltip('Show information about Harvester')
        )
        button_about.toggle()
        observers.append(button_about)

        #
        self._widget_device_list = ComboBox(self)
        self._widget_device_list.setSizeAdjustPolicy(
            QComboBox.AdjustToContents
        )
        shortcut_key = 'Ctrl+Shift+d'
        shortcut = QShortcut(QKeySequence(shortcut_key), self)

        def show_popup():
            self._widget_device_list.showPopup()

        shortcut.activated.connect(show_popup)
        self._widget_device_list.setToolTip(
            compose_tooltip('Select a device to connect', shortcut_key)
        )
        observers.append(self._widget_device_list)
        for d in self.harvester_core.device_info_list:
            self._widget_device_list.addItem(d)