Custom field in lesson

Hi, I want to add a custom field to lessons using the API (https://docs.themeum.com/tutor-lms/developer-documentation/register-custom-fields/#available-field-registration-options), but the ‘uploader’ field doesn’t seem to have a ‘multiple’ option. Here is my code:

Tutor.CourseBuilder.Curriculum.Lesson.registerField("bottom_of_sidebar", {
name: "upload_files_field",
type: "uploader",
label: "Subir coso",
priority: 2,
multiple: true,
});

Does this option exist or not?