In the docs there's text next to the name of every field of a class/component/etc. describing its type. The thing is this text is white (#ffffff) on a white (#fff) background effectively hiding it if it's not highlighted.
This actually cost me quite some time because I wasn't aware I was able to pass a function instead of a string for a specific field through which I was able to solve the problem at hand.
Here's an example: https://www.telerik.com/kendo-angular-ui/components/dataquery/api/FilterDescriptor/, I've also included screenshots of what I'm seeing.