This method can be used to set the padding pixels between different groups.
The example on the left is using the default padding 0 and the example on the right has padding 5 px.
The pad option is useful for create white space seperators between different values of the parts.
For other options and examples, check VizJS
Modified http://vizjs.org/viz.v1.1.0.min.js to a secure url
https://d3js.org/d3.v4.min.js
https://vizjs.org/viz.v1.1.0.min.js