from opaque_keys.edx.django.models import CourseKeyField from django.db import models class MyModel(models.Model): course_key = CourseKeyField()In this example, we create a simple model with a single field, `course_key`, which is of the `CourseKeyField` type. This field can be used to store edX course keys. The `opaque_keys` library is a package for creating and working with opaque keys, which are keys that are not easily understandable or predictable by humans. The edX platform uses opaque keys to identify courses, making it difficult for students to guess the keys of other courses they are not enrolled in.