片側だけに分布の波が書かれた図形
#memo
Violin Plotsと呼ぶらしい
https://plotly.com/python/violin/
https://github.com/jorvlan/open-visualizations/raw/master/R/figure5c.png
https://gyazo.com/ec8ed041cf70f2b1e95202ce71e59297
https://gyazo.com/e66055266372dbcdbfda7173a660e44d