Explanation now uses 'member' rather than 'athlete', since latter is not a schema.org property currently.
Adding a set of examples for Role, based on
https://docs.google.com/a/google.com/document/d/1RSe6zr--DuIk9AzJyuMfOzw4_kc-DwPbgx2IH9LiCzs/edit?disco=AAAAAJnB6Ew#