add python decorator

Author: rl-utility-man

doc/python/horizontal-bar-charts.md

@@ -220,7 +220,7 @@ fig.show()
 
 Diverging bar charts offer two imperfect options for responses that are neither positive nor negative:  put them in a separate column, as in this example or omit them as in the example above.  That leaves the unreported neutral value implicit when the categories add to 100%,   Jonathan Schwabish discusses this on page 92-97 of  _Better Data Visualizations_.
 
-```
+```python
 import pandas as pd
 import plotly.graph_objects as go