Python (PyQt5) При нажатии на кнопку Cancel выдаёт ошибку

НИКОГДА НЕ ИЗМЕНЯЙТЕ код, сгенерированный Qt Designer, НИКОГДА.
Создайте другой класс, который наследуется от соответствующего виджета, и используйте созданный класс для его заполнения.

q1411037_main.py

from PyQt5 import QtCore, QtGui, QtWidgets

from q1411037_signals import NewWindowChoiceMic


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(250, 420)
        MainWindow.setMinimumSize(QtCore.QSize(250, 420))
        MainWindow.setMaximumSize(QtCore.QSize(250, 420))
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 250, 22))
        self.menubar.setObjectName("menubar")
        self.settings = QtWidgets.QMenu(self.menubar)
        self.settings.setObjectName("settings")
        self.microphone_settings = QtWidgets.QMenu(self.settings)
        self.microphone_settings.setObjectName("microphone_settings")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
        self.chose_microphone = QtWidgets.QAction(MainWindow)
        self.chose_microphone.setObjectName("chose_microphone")
        self.microphone_settings.addAction(self.chose_microphone)
        self.settings.addAction(self.microphone_settings.menuAction())
        self.menubar.addAction(self.settings.menuAction())

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle("MainWindow")
        self.settings.setTitle(_translate("MainWindow", 
            "Настройки"))
        self.microphone_settings.setTitle(_translate("MainWindow", 
            "Микрофон"))
        self.chose_microphone.setText(_translate("MainWindow", 
            "Выбор устройства..."))


class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)
        
        self.label = QtWidgets.QLabel(self.centralwidget)   # + для теста
        self.label.setAlignment(QtCore.Qt.AlignCenter)      # + для теста
        layout = QtWidgets.QHBoxLayout(self.centralwidget)  # + для теста
        layout.addWidget(self.label)                        # + для теста
        
        self.newWindowChoiceMic = NewWindowChoiceMic(self)                # !!! +++
        
#        self.add_funk()
#    def add_funk(self):
#        self.chose_microphone.triggered.connect(lambda: signals.choice_micro(True))

        self.chose_microphone.triggered.connect(
            lambda: self.newWindowChoiceMic.choice_micro(True)            # !!! +++
        )
        

if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

q1411037_signals.py

from PyQt5 import QtCore, QtGui, QtWidgets
import speech_recognition as SR

from q1411037_choise import Ui_Choise_mic


class NewWindowChoiceMic(QtWidgets.QWidget, Ui_Choise_mic):
    chosen_mic = ""                                                       # !!! +++

    def __init__(self, parent):                                           # + parent
#        super(NewWindowChoiceMic, self).__init__(parent)
        super(NewWindowChoiceMic, self).__init__()                        # - parent
        
        self.setupUi(self)
        
        self.parent = parent                                              # +++
        
        self.add_funk()
        self.add_funk_btn()
        
# -----------------> vvvv
    def choice_micro(self, signal):                                       # !!!
        if signal:
# --------> vvvv
            self.show()
        else:
# --------> vvvv
            self.hide()        
 
    def add_funk(self):
        list_mic = SR.Microphone().list_microphone_names()
        self.comboBox.addItems(list_mic)
        
#        if self.comboBox.currentTextChanged.connect(lambda: self.text_changed()):
#            self.text_changed()
        self.comboBox.currentTextChanged.connect(self.text_changed)           # !!!

# -----------------------> vvvv
    def text_changed(self, text):
        print(f'{text}') # 
#        global chosen_mic
#        self.chosen_mic = SR.Microphone.list_microphone_names().index(
#            self.comboBox.currentText())
        self.chosen_mic = text

    def add_funk_btn(self):
        self.ok.clicked.connect(self.Ok)
        self.cancel.clicked.connect(self.Cansel)

    def Cansel(self): #!!!
#        signals.choice_micro(False)
# ----> vvvv
        self.choice_micro(False)

    def Ok(self):
        # *часть для сохранения в json файл (удалена за ненадобностью в демонстрации)
#        signals.choice_micro(False)
# ----> vvvv
        self.choice_micro(False) 
        
        self.parent.label.setText(f'{self.comboBox.currentText()}')        # для теста
     

q1411037_choise.py

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_Choise_mic(object):
    def setupUi(self, Choise_mic):
        Choise_mic.setObjectName("Choise_mic")
        Choise_mic.resize(500, 70)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Fixed, 
            QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(
            Choise_mic.sizePolicy().hasHeightForWidth())
        Choise_mic.setSizePolicy(sizePolicy)
        Choise_mic.setMinimumSize(QtCore.QSize(500, 70))
        Choise_mic.setMaximumSize(QtCore.QSize(500, 70))
        self.comboBox = QtWidgets.QComboBox(Choise_mic)
        self.comboBox.setGeometry(QtCore.QRect(10, 10, 481, 22))
        self.comboBox.setObjectName("comboBox")
        self.ok = QtWidgets.QPushButton(Choise_mic)
        self.ok.setGeometry(QtCore.QRect(10, 40, 75, 24))
        self.ok.setObjectName("ok")
        self.cancel = QtWidgets.QPushButton(Choise_mic)
        self.cancel.setGeometry(QtCore.QRect(420, 40, 75, 24))
        self.cancel.setObjectName("cancel")

        self.retranslateUi(Choise_mic)
        QtCore.QMetaObject.connectSlotsByName(Choise_mic)

    def retranslateUi(self, Choise_mic):
        _translate = QtCore.QCoreApplication.translate
        Choise_mic.setWindowTitle(_translate("Choise_mic", "Выбор микрофона"))
        self.ok.setText(_translate("Choise_mic", "Ок"))
        self.cancel.setText(_translate("Choise_mic", "Отмена"))