@SubtypeOf(value={}) @DefaultInUncheckedCodeFor(value={RETURN,UPPER_BOUND}) @Documented @Retention(value=RUNTIME) @Target(value={TYPE_USE,TYPE_PARAMETER}) public @interface Nullable
Nullable is a type annotation that indicates that the value is not known to be non-null
 (see NonNull). Only if an expression has a Nullable type may it be assigned
 null.
 This annotation is associated with the AbstractNullnessChecker.
NonNull, 
MonotonicNonNull, 
AbstractNullnessChecker