text: Title: HeatMapWithTime can not work
  Body: #### Please add a code sample or a nbviewer link, copy-pastable if possible
  
  ```python
  # Your code here
  HeatMapWithTime can not work
  version python:3.7.4
  ```
  #### Problem description
  
  https://nbviewer.jupyter.org/github/python-visualization/folium/blob/master/examples/HeatMapWithTime.ipynb
  this demo can not work
  
  #### Expected Output
  
  #### Output of ``folium.__version__``
  '0.10.0'