improve timeline and treelayercontrol docs

Author: Conengmo

docs/user_guide/plugins/timeline.md

@@ -28,6 +28,8 @@ Depending on your input geojson, one plugin may be more convenient than the othe
 The `Timeline` plugin can only show data from the past. If you want live updates,
 you need the `Realtime` plugin.
 
+### Example of Timeline and TimelineSlider
+
 ```{code-cell} ipython3
 import folium
 from folium.utilities import JsCode

docs/user_guide/plugins/treelayercontrol.md

@@ -20,7 +20,6 @@ from folium.plugins.treelayercontrol import TreeLayerControl
 from folium.features import Marker
 
 m = folium.Map(location=[46.603354, 1.8883335], zoom_start=5)
-osm = folium.TileLayer("openstreetmap").add_to(m)
 
 overlay_tree = {
     "label": "Points of Interest",
@@ -71,5 +70,7 @@ overlay_tree = {
     ]
 }
 
-control = TreeLayerControl(overlay_tree=overlay_tree).add_to(m)
+TreeLayerControl(overlay_tree=overlay_tree).add_to(m)
+
+m
 ```