Annotation to inform users of a package, class or method's intended audience. Currently the audience can be Public, LimitedPrivate or Private.
All public classes must have InterfaceAudience annotation.

• Public classes that are not marked with this annotation must be considered by default as Private.
• External applications must only use classes that are marked Public. Avoid using non public classes as these classes could be removed or change in incompatible ways.
• Hadoop projects must only use classes that are marked LimitedPrivate or Public
• Methods may have a different annotation that it is more restrictive compared to the audience classification of the class. Example: A class might be Public, but a method may be LimitedPrivate