If radio is true, the cell renderer renders a radio toggle (i.
e. a toggle in a group of mutually-exclusive toggles). If false, it renders a check toggle (a standalone boolean option). This can be set globally for the cell renderer, or changed just before rendering each cell in the model (for `GtkTreeView`, you set up a per-row setting using `GtkTreeViewColumn` to associate model columns with cell renderer properties).
| this |
a `GtkCellRendererToggle` |
| radio |
true to make the toggle look like a radio button |