@Target(value={METHOD,PARAMETER,FIELD}) @Retention(value=RUNTIME) @Documented @Nonnull(when=MAYBE) @TypeQualifierNickname public @interface Nullable
null under some circumstance. Leverages JSR 305 meta-annotations to
 indicate nullability in Java to common tools with JSR 305 support and used by Kotlin to
 infer nullability of Reactor API.
 Should be used at parameter, return value, and field level.
 Methods overrides should repeat parent @Nullable annotations unless they behave
 differently.
 
Can be used in association with NonNullApi to override the default
 non-nullable semantic to nullable.
NonNullApi, 
NonNull