How to use the pandasgui.gui.PandasGUI.NavWidget function in pandasgui

def setupUI(self):
        """
        Creates and adds all widgets to GUI.
        """

        # This holds the DataFrameExplorer for each DataFrame
        self.stacked_widget = QtWidgets.QStackedWidget()

        # Make the navigation bar
        self.nav_tree = self.NavWidget(self)
        # Creates the headers.
        self.nav_tree.setHeaderLabels(["Name", "Shape"])
        self.nav_tree.itemSelectionChanged.connect(self.nav_clicked)

        for df_name in store.data.keys():
            df_object = store.data[df_name]["dataframe"]
            self.add_dataframe(df_name, df_object)

        # Make splitter to hold nav and DataFrameExplorers
        self.splitter = QtWidgets.QSplitter(QtCore.Qt.Horizontal)
        self.splitter.addWidget(self.nav_tree)
        self.splitter.addWidget(self.stacked_widget)

        self.splitter.setCollapsible(0, False)
        self.splitter.setCollapsible(1, False)
        self.splitter.setStretchFactor(0, 0)