title: How to plot Time Series Heatmap with Python?
body: <p><em>I want to draw a chart with x-axis as timeline, y-axis as its value and the color will indicate its frequency. The higher the frequency, the deeper the color is.</em> </p>
  
  <p><img src="https://i.stack.imgur.com/vETcn.png" alt="Here is the chart I want to draw"></p>