Python 如何在cartopy地图上缩放时剪裁子地块边界外的文本？

我使用带有cartopy包的matplotlib在matplotlib图的子图中显示巴基斯坦地图及其城市名称，如图1所示。 但我的问题是，当我放大子地块以查看更多细节时，一切正常，但绘制的文本（城市名称）显示在子地块边界之外，如何剪裁外部文本

这是我在卡通地图上绘制城市名称的代码

    def draw_cities(self, extent, axis):

        cities_df = pd.read_csv('assets/maps/cities.csv')

        # axis.plot(lons, lats, markersize=5, marker='o', linestyle='', color='#b30909', transform=ccrs.PlateCarree(),
        #           label='ASOS Station')

        self.cities_plot = axis.scatter(cities_df.lng.values, cities_df.lat.values,
                                       color='red', marker='.', transform=ccrs.PlateCarree())
        transform = ccrs.PlateCarree()._as_mpl_transform(axis)  # set transform for annotations
        self.cities_text = []
        # text annotations
        for lat_s, lon_s, name_s in zip(cities_df.lat.values, cities_df.lng.values, cities_df.city.values):  # loop through lats/lons/names
            if lon_s > extent[0] and lon_s < extent[1] and lat_s > extent[2] and lat_s < extent[3]:
                text = axis.text(lon_s, lat_s, name_s, {'color': 'r', 'fontsize': 6},
                                 horizontalalignment='center', verticalalignment='bottom',
                                 clip_on=True, transform=transform)

                self.cities_text.append(text)

这是放大前的输出（图1），放大效果良好：

这是放大后的输出（图2），我想剪辑子地块边界外以蓝色圆圈显示的文本：

    def zoom_factory(self, ax, base_scale=2.):
        def zoom_fun(event):
            # get the current x and y limits
            cur_xlim = ax.get_xlim()
            cur_ylim = ax.get_ylim()
            cur_xrange = (cur_xlim[1] - cur_xlim[0]) * .5
            cur_yrange = (cur_ylim[1] - cur_ylim[0]) * .5
            xdata = event.xdata  # get event x location
            ydata = event.ydata  # get event y location
            if event.button == 'up':
                # deal with zoom in
                scale_factor = 1 / base_scale
            elif event.button == 'down':
                # deal with zoom out
                scale_factor = base_scale
            else:
                # deal with something that should never happen
                scale_factor = 1
                print(event.button)
            # set new limits

            ax.figure.canvas.toolbar.push_current() # resolve home button issue

            # zoom for better user erxperince
            ax.set_xlim([xdata - (xdata - cur_xlim[0]) / scale_factor,
                         xdata + (cur_xlim[1] - xdata) / scale_factor])
            ax.set_ylim(
                [ydata - (ydata - cur_ylim[0]) / scale_factor, ydata + (cur_ylim[1] - ydata) / scale_factor])

            self.Canvas1.draw_idle()

        fig = ax.get_figure()  # get the figure of interest
        # attach the call back
        fig.canvas.mpl_connect('scroll_event', zoom_fun)

        # return the function
        return zoom_fun