Диалог в Qt Designer

class MyWidget(..):
 
def func_with_par(self, par):
    …
 
def func_dialog(self):
    dialog_wgt = My_dialog()
    self._my_value = dialog_wgt.ui…     dialog_wgt.ui.myButton.clicked.connect(self.func_with_par)
    dialog_wgt.exec()
 
class My_dialog(…):
    def init(self):
        super().__init__()
        self._setup_ui()
 
    def _setup_ui(self):
        self.ui = Ui_My_dialog()
        self.ui.setupUi(self)

import sys
from PyQt5 import QtWidgets
 
 
CONFIGURATION = {
    "VOLUME": 12,
}
 
class ChangeVolumeDialog(QtWidgets.QDialog):
    def __init__(self, parent: QtWidgets.QWidget = None):
        QtWidgets.QDialog.__init__(self, parent)
        self.setWindowTitle("Введите")
 
        self.volume_editor = QtWidgets.QSpinBox(self)
        self.volume_editor.setRange(0, 100)
        self.volume_editor.setValue(CONFIGURATION["VOLUME"])
 
        self.volume_change = QtWidgets.QPushButton("Применить", self)
        self.volume_change.clicked.connect(self.change_volume_event)
 
        layout = QtWidgets.QFormLayout(self)
        layout.addRow(self.tr("Значение громкости"), self.volume_editor)
        layout.addRow(self.volume_change)
 
        self.show()
 
    def change_volume_event(self):
        CONFIGURATION["VOLUME"] = self.volume_editor.value()
 
 
class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent: QtWidgets.QWidget = None):
        QtWidgets.QMainWindow.__init__(self, parent)
 
        screen = QtWidgets.QDesktopWidget().availableGeometry()
        self.setGeometry(int(screen.width()/4), int(screen.height()/4),
                         int(screen.width()/2), int(screen.height()/2))
 
        self.setWindowTitle("The Dialog Probe v0.002")
        
        file_menu = self.menuBar().addMenu("Файл")
        file_menu.addAction("Громкость", self.open_change_volume_dialog, shortcut="Ctrl+P")
        file_menu.addAction("Выход", self.close, shortcut="Ctrl+Q")
 
    def open_change_volume_dialog(self):
        ChangeVolumeDialog(self).show()
 
    
if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    mainWin = MainWindow()
    mainWin.show()
    sys.exit(app.exec_())