title: Python: Folium HTML Popups
body: <p>How can I add a <code>html</code> popup to a <code>Folium choropleth</code> map?</p>
  <p>I have no problems doing this for <code>Folium.CircleMarker</code> but cannot find a way for Choropleth maps.</p>
  <p>My approach so far is:</p>
  <pre><code>   import folium
     import pandas as pd
  
  
  m = folium.Map(location=[LAT, LONG], tiles = 'Stamen Terrain', zoom_start=8)
  
  
  mm = folium.Choropleth(
      geo_data=polygons,
      name='Number of Points in Shape File',
      data=df,
      columns=['shape_name', 'number_of_points'],
      key_on='feature.properties.shape_name',
      fill_color='Greens',
      highlight=True,
      smooth_factor=0,
      threshold_scale=[0, 2, 4, 6, 8, 10, 15, 20, 35, 50],
      legend_name= 'Number of Points within Polygon').add_to(m)
  </code></pre>
  <p>Here comes the part of adding a tooltip when hovering over a plotted shapefile from <code>polygons</code>.</p>
  <pre><code>mm.geojson.add_child(folium.features.GeoJsonTooltip(
          fields=['shape_name', 'number_of_points'],
          aliases=['Polygon Name: ', 'Number of Points within Boundary: '],
          style=('background-color: grey; color: white;')
          ))
  </code></pre>
  <p>How can I add a html popup when hovering over one of the plotted shapefiles in Folium, e.g. for incorporating images?</p>
  <p>Superimposing the plotted data with a <code>PolyLine</code> Feature?</p>