<NME> webdriver_example.py
<BEF> ADDFILE
<MSG> docs(python): add example of using webdriver to access Neuroglancer state directly

<DFF> @@ -0,0 +1,20 @@
+import neuroglancer
+import neuroglancer.webdriver
+
+viewer = neuroglancer.Viewer()
+with viewer.txn() as s:
+    s.layers['image'] = neuroglancer.ImageLayer(
+        source='precomputed://gs://neuroglancer-janelia-flyem-hemibrain/emdata/clahe_yz/jpeg',
+    )
+    s.layers['segmentation'] = neuroglancer.SegmentationLayer(
+        source='precomputed://gs://neuroglancer-janelia-flyem-hemibrain/v1.1/segmentation',
+    )
+
+webdriver = neuroglancer.webdriver.Webdriver(viewer, headless=False)
+
+
+def get_loading_progress():
+    return webdriver.driver.execute_script('''
+const userLayer = viewer.layerManager.getLayerByName("segmentation").layer;
+return userLayer.renderLayers.map(x => x.layerChunkProgressInfo)
+ ''')

docs(python): add example of using webdriver to access Neuroglancer state directly