Container of information related to one possible annotation that can
be used in a labeling task. For example, an image classification
task where images are labeled as dog or cat must reference
an AnnotationSpec for dog and an AnnotationSpec for cat.
Required. The display name of the
AnnotationSpec. Maximum of 64 characters.
Optional. User-provided description of the
annotation specification. The description can be
up to 10,000 characters long.