Adding custom field to lesson

Hi, I have been able to add a custom field to the course builder using your docs here

https://docs.themeum.com/tutor-lms/developer-documentation/register-custom-fields/

What do I change here to make the field appear for the lesson and not the course itself?

if (typeof Tutor !== “undefined” && Tutor.CourseBuilder) {

and here

Tutor.CourseBuilder.Basic.registerField(“after_description”, {

I tried changing Course to Lesson but I still cant see the field in the lesson builder.

Thanks