thank you, i missed that in the documentation.
according to this link, i should be able to use the following:

The dataSource can be an array of strings/numbers or objects where the attributes represent the properties of a List Item. For example label, value, group.

however, i am unable to see the group here:  https://codepen.io/edwardsmarkf/pen/VwKwogP
please let me know what i am doing incorrectly.