QScrollArea doesn't work. What to do?

Question

Python

When creating a ScrollArea, just a gray


main.py window:

from PyQt5 import QtWidgets
from notes import Ui_Main_Window


class Win(QtWidgets.QMainWindow):
    def __init__(self):
        global user
        super().__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        #   create ScrollArea
        sa = QtWidgets.QScrollArea()
        sa.resize(200, 200)
        sa.setWidget(self.ui.tabWidget)


app = QtWidgets.QApplication([])
appl = Win()
appl.show()

exit(app.exec())

notes.py (design):

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(291, 440)
        MainWindow.setStyleSheet("background: rgb(50, 50, 50);")
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.tabWidget = QtWidgets.QTabWidget(self.centralwidget)
        self.tabWidget.setGeometry(QtCore.QRect(0, 0, 291, 441))
        self.tabWidget.setStyleSheet("QTabBar::tab{\n"
"    border-radius: 10px;\n"
"    margin: 5px;\n"
"    padding: 10px;\n"
"    background: white;\n"
"}\n"
"QTabBar::tab::selected {\n"
"    background: orange;\n"
"    color: white;\n"
"}")
        self.tabWidget.setObjectName("tabWidget")
        self.notes = QtWidgets.QWidget()
        self.notes.setObjectName("notes")
        self.label_4 = QtWidgets.QLabel(self.notes)
        self.label_4.setGeometry(QtCore.QRect(10, 10, 261, 111))
        self.label_4.setStyleSheet("border: 1px solid white;\n"
"color: white;\n"
"font-size: 15px;")
        self.label_4.setAlignment(QtCore.Qt.AlignLeading|QtCore.Qt.AlignLeft|QtCore.Qt.AlignTop)
        self.label_4.setObjectName("label_4")
        self.label_5 = QtWidgets.QLabel(self.notes)
        self.label_5.setGeometry(QtCore.QRect(10, 140, 261, 111))
        self.label_5.setStyleSheet("border: 1px solid white;\n"
"color: white;\n"
"font-size: 15px;")
        self.label_5.setAlignment(QtCore.Qt.AlignLeading|QtCore.Qt.AlignLeft|QtCore.Qt.AlignTop)
        self.label_5.setObjectName("label_5")
        self.label_6 = QtWidgets.QLabel(self.notes)
        self.label_6.setGeometry(QtCore.QRect(10, 270, 261, 111))
        self.label_6.setStyleSheet("border: 1px solid white;\n"
"color: white;\n"
"font-size: 15px;")
        self.label_6.setAlignment(QtCore.Qt.AlignLeading|QtCore.Qt.AlignLeft|QtCore.Qt.AlignTop)
        self.label_6.setObjectName("label_6")
        self.tabWidget.addTab(self.notes, "")
        self.add_notes = QtWidgets.QWidget()
        self.add_notes.setObjectName("add_notes")
        self.pushButton = QtWidgets.QPushButton(self.add_notes)
        self.pushButton.setGeometry(QtCore.QRect(80, 340, 121, 31))
        self.pushButton.setStyleSheet("QPushButton {\n"
"background: black;\n"
"color: white;\n"
"border:1px solid white;\n"
"border-radius: 10px;\n"
"}")
        self.pushButton.setObjectName("pushButton")
        self.lineEdit = QtWidgets.QLineEdit(self.add_notes)
        self.lineEdit.setGeometry(QtCore.QRect(40, 80, 201, 41))
        self.lineEdit.setStyleSheet("background: black;\n"
"color: white;\n"
"border:1px solid white;\n"
"border-radius: 10px;")
        self.lineEdit.setObjectName("lineEdit")
        self.label = QtWidgets.QLabel(self.add_notes)
        self.label.setGeometry(QtCore.QRect(50, 60, 71, 16))
        self.label.setStyleSheet("color: white;")
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.add_notes)
        self.label_2.setGeometry(QtCore.QRect(30, 10, 211, 31))
        self.label_2.setLayoutDirection(QtCore.Qt.LeftToRight)
        self.label_2.setStyleSheet("color: white;\n"
"font-size: 20px;")
        self.label_2.setLineWidth(0)
        self.label_2.setMidLineWidth(0)
        self.label_2.setAlignment(QtCore.Qt.AlignCenter)
        self.label_2.setObjectName("label_2")
        self.label_3 = QtWidgets.QLabel(self.add_notes)
        self.label_3.setGeometry(QtCore.QRect(50, 140, 101, 16))
        self.label_3.setStyleSheet("color: white;")
        self.label_3.setObjectName("label_3")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.add_notes)
        self.lineEdit_2.setGeometry(QtCore.QRect(40, 160, 201, 141))
        self.lineEdit_2.setStyleSheet("background: black;\n"
"color: white;\n"
"border:1px solid white;\n"
"border-radius: 10px;")
        self.lineEdit_2.setText("")
        self.lineEdit_2.setAlignment(QtCore.Qt.AlignLeading|QtCore.Qt.AlignLeft|QtCore.Qt.AlignTop)
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.tabWidget.addTab(self.add_notes, "")
        MainWindow.setCentralWidget(self.centralwidget)

        self.retranslateUi(MainWindow)
        self.tabWidget.setCurrentIndex(0)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.label_4.setText(_translate("MainWindow", "Сварить суп"))
        self.label_5.setText(_translate("MainWindow", "Сделать ещё что-то"))
        self.label_6.setText(_translate("MainWindow", "И ещё что-то..."))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.notes), _translate("MainWindow", "Заметки"))
        self.pushButton.setText(_translate("MainWindow", "Сохранить"))
        self.label.setText(_translate("MainWindow", "Заголовок:"))
        self.label_2.setText(_translate("MainWindow", "Создание заметки"))
        self.label_3.setText(_translate("MainWindow", "Текст заметки:"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.add_notes), _translate("MainWindow", "Добавить заметку"))

How to make notes scroll?