Access existing viewer from python about neuroglancer HOT 3 OPEN

import panel as pn
import neuroglancer

pn.extension()

class NeuroglancerViewerApp(pn.viewable.Viewer):
    DEMO_URL = 'https://neuroglancer-demo.appspot.com/#!%7B%22dimensions%22:%7B%22x%22:%5B6.000000000000001e-9%2C%22m%22%5D%2C%22y%22:%5B6.000000000000001e-9%2C%22m%22%5D%2C%22z%22:%5B3.0000000000000004e-8%2C%22m%22%5D%7D%2C%22position%22:%5B5029.42333984375%2C6217.5849609375%2C1182.5%5D%2C%22crossSectionScale%22:3.7621853549999242%2C%22projectionOrientation%22:%5B-0.05179581791162491%2C-0.8017329573631287%2C0.0831851214170456%2C-0.5895944833755493%5D%2C%22projectionScale%22:4699.372698097029%2C%22layers%22:%5B%7B%22type%22:%22image%22%2C%22source%22:%22precomputed://gs://neuroglancer-public-data/kasthuri2011/image%22%2C%22tab%22:%22source%22%2C%22name%22:%22original-image%22%7D%2C%7B%22type%22:%22image%22%2C%22source%22:%22precomputed://gs://neuroglancer-public-data/kasthuri2011/image_color_corrected%22%2C%22tab%22:%22source%22%2C%22name%22:%22corrected-image%22%7D%2C%7B%22type%22:%22segmentation%22%2C%22source%22:%22precomputed://gs://neuroglancer-public-data/kasthuri2011/ground_truth%22%2C%22tab%22:%22source%22%2C%22selectedAlpha%22:0.63%2C%22notSelectedAlpha%22:0.14%2C%22segments%22:%5B%223208%22%2C%224901%22%2C%2213%22%2C%224965%22%2C%224651%22%2C%222282%22%2C%223189%22%2C%223758%22%2C%2215%22%2C%224027%22%2C%223228%22%2C%22444%22%2C%223207%22%2C%223224%22%2C%223710%22%5D%2C%22name%22:%22ground_truth%22%7D%5D%2C%22layout%22:%224panel%22%7D'

    def __init__(self, **params):
        super().__init__(**params)
        self.viewer = neuroglancer.Viewer()
        self._setup_ui_components()
        self._configure_viewer()
        self._setup_callbacks()

    def _setup_ui_components(self):
        self.url_input = pn.widgets.TextInput(
            placeholder="Enter a Neuroglancer URL and click Load", name='Input URL', width=700
        )
        self.load_button = pn.widgets.Button(name="Load", button_type="primary", width=75)
        self.demo_button = pn.widgets.Button(name="Demo", button_type="warning", width=75)
        self.json_pane = pn.pane.JSON({}, theme='light', depth=2, name='Viewer State', height=600, width=400)
        self.shareable_url_pane = pn.pane.Markdown("**Shareable URL:**")
        self.local_url_pane = pn.pane.Markdown("**Local URL:**")
        self.iframe = pn.pane.HTML(sizing_mode='stretch_both', min_height=700, min_width=700)

    def _configure_viewer(self):
        self.update_local_url()
        self.update_iframe_with_local_url()

    def _setup_callbacks(self):
        self.load_button.on_click(self._on_load_button_clicked)
        self.demo_button.on_click(self._on_demo_button_clicked)
        self.viewer.shared_state.add_changed_callback(self._on_viewer_state_changed)

    def _on_demo_button_clicked(self, event):
        self.url_input.value = self.DEMO_URL
        self._load_neuroglancer_state_from_url(self.url_input.value)

    def _on_load_button_clicked(self, event):
        self._load_neuroglancer_state_from_url(self.url_input.value)

    def _load_neuroglancer_state_from_url(self, url):
        try:
            new_state = neuroglancer.parse_url(url)
            self.viewer.set_state(new_state)
        except Exception as e:
            print(f"Error loading Neuroglancer state: {e}")

    def _on_viewer_state_changed(self):
        self.update_shareable_url()
        self.update_json_pane()

    def update_shareable_url(self):
        shareable_url = neuroglancer.to_url(self.viewer.state)
        self.shareable_url_pane.object = self._generate_details_markup("Shareable URL", shareable_url)

    def update_local_url(self):
        self.local_url_pane.object = self._generate_details_markup("Local URL", self.viewer.get_viewer_url())

    def update_iframe_with_local_url(self):
        self.iframe.object = f'<iframe src="{self.viewer.get_viewer_url()}" width="700" height="700"></iframe>'

    def update_json_pane(self):
        self.json_pane.object = self.viewer.state.to_json()

    def _generate_details_markup(self, title, url):
        return f"""
            <details>
                <summary><b>{title}:</b></summary>
                <a href="{url}" target="_blank">{url}</a>
            </details>
        """

    def __panel__(self):
        controls_layout = pn.Column(
            pn.Row(self.demo_button, self.load_button),
            pn.Row(self.url_input))
        links_layout = pn.Column(self.local_url_pane, self.shareable_url_pane)
        return pn.Column(
            controls_layout,
            links_layout,
            pn.Row(self.iframe, self.json_pane))

app = NeuroglancerViewerApp()
app.servable()