Choropleth: Fix infinite callback loop (#523)

Author: omanges

examples/Choropleth.ipynb

@@ -72,17 +72,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "layer.style_callback = compute_style"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "m.add_layer(layer_callback)\n",
-    "m"
+    "layer.style_callback=compute_style"
    ]
   },
   {

ipyleaflet/leaflet.py

@@ -547,7 +547,7 @@ def _validate_style_callback(self, proposal):
             raise TraitError('style_callback should be callable (functor/function/lambda)')
         return proposal.value
 
-    @observe('data', 'style', 'style_callback')
+    @observe('style', 'style_callback')
     def _update_data(self, change):
         self.data = self._get_data()