graph style

option for changing the graph style
- scatterplot 
- bubble plot 
- 2d density plot 
- bubble map 
- choropleth map 
- tree plot 
- boxplot 
- violin 
- venn diagram 
- stacked barplot 
- area plot 
- streamchart 
- stacked area plot 
- parrallel plot 
- barplot 
- lollipop plot 
- chord diagram 
- sankey diagram 