how to add a button to smart table

how can i add a button in smart table.
i found this link https://akveo.github.io/ng2-smart-table/#/examples/custom-editors-viewers where they integrated the button inside the cell, but i couldn' find the code.
i tried this code but it doesn't work
` columns:

{
stat:
{
title: 'stat',
type: 'html',
valuePrepareFunction: (value) => {
return `bouton`;
}
},
}`