def display_eventtype(self):
        """Read the list of event types in the annotations and update widgets.
        """
        if self.annot is not None:
            event_types = sorted(self.annot.event_types, key=str.lower)
        else:
            event_types = []

        self.idx_eventtype.clear()

        evttype_group = QGroupBox('Event Types')
        layout = QVBoxLayout()
        evttype_group.setLayout(layout)
        
        self.check_all_eventtype = check_all = QCheckBox('All event types')
        check_all.setCheckState(Qt.Checked)
        check_all.clicked.connect(self.toggle_eventtype)
        layout.addWidget(check_all)

        self.idx_eventtype_list = []
        for one_eventtype in event_types:
            self.idx_eventtype.addItem(one_eventtype)
            item = QCheckBox(one_eventtype)
            layout.addWidget(item)
            item.setCheckState(Qt.Checked)
            item.stateChanged.connect(self.update_annotations)
            item.stateChanged.connect(self.toggle_check_all_eventtype)
            self.idx_eventtype_list.append(item)

        self.idx_eventtype_scroll.setWidget(evttype_group)
Read the list of event types in the annotations and update widgets.