PYQT QTableWidgetItem.flags() can not effective!

from PyQt5.QtWidgets import QApplication,QTableWidgetItem,QTableWidget,QWidget,QHBoxLayout,QHeaderView
from PyQt5.QtCore import Qt
import sys
class test_bug(QWidget):
    def __init__(self):
        super().__init__()
        self.setup_ui()
    def setup_ui(self):
        self.resize(500,350)
        table = QTableWidget()
        table.setColumnCount(3)
        table.setRowCount(4)
        table.setColumnWidth(0,150)
        table.setColumnWidth(1,150)
        for x in range(4):
            table.setRowHeight(x,50)
        table.horizontalHeader().setSectionResizeMode(2,QHeaderView.Stretch)
        qbox = QHBoxLayout()
        qbox.addWidget(table)
        item1 = QTableWidgetItem('NoItemFlags')
        item1.setFlags(Qt.NoItemFlags)
        item2 = QTableWidgetItem('ItemIsSelectable')
        item2.setFlags(Qt.ItemIsSelectable)
        item3 = QTableWidgetItem('ItemIsEditable')
        item3.setFlags(Qt.ItemIsEditable)
        item4 = QTableWidgetItem('ItemIsDragEnabled')
        item4.setFlags(Qt.ItemIsDragEnabled)
        item5 = QTableWidgetItem('ItemIsDropEnabled')
        item5.setFlags(Qt.ItemIsDropEnabled)
        item6 = QTableWidgetItem('ItemIsUserCheckable')
        item6.setFlags(Qt.ItemIsUserCheckable)
        item7 = QTableWidgetItem('ItemIsEnabled')
        item7.setFlags(Qt.ItemIsEditable)
        item8 = QTableWidgetItem('ItemIsAutoTristate')
        item8.setFlags(Qt.ItemIsAutoTristate)
        item9 = QTableWidgetItem('ItemIsTristate')
        item9.setFlags(Qt.ItemIsTristate)
        item10 = QTableWidgetItem('ItemNeverHasChildren')
        item10.setFlags(Qt.ItemNeverHasChildren)
        item11 = QTableWidgetItem('ItemIsUserTristate')
        item11.setFlags(Qt.ItemIsUserTristate)
        item12 = QTableWidgetItem('not set')
        table.setItem(0,0,item1)
        table.setItem(0,1,item2)
        table.setItem(0,2,item3)
        table.setItem(1,0,item4)
        table.setItem(1,1,item5)
        table.setItem(1,2,item6)
        table.setItem(2,0,item7)
        table.setItem(2,1,item8)
        table.setItem(2,2,item9)
        table.setItem(3,0,item10)
        table.setItem(3,1,item11)
        table.setItem(3,2,item12)
        self.setLayout(qbox)
        self.show()
if __name__ == '__main__':
    app = QApplication(sys.argv)
    ui = test_bug()
    sys.exit(app.exec_())