code: public boolean addAnnotation(final Class<? extends Annotation> clazz) {
          if (disregarding && marked.add(clazz)) {
              initializeCachedFields();
              return true;
          }
          return false;
      }
docs: Adds an annotation to the annotations that are considered by this serializer.
  <p/>
  <b>Important</b>: This will not have an effect if the serializer was configured
  to exclusively serialize annotated fields by setting {@code disregarding} to
  {@code false}. This is similar to the contract of this serializer's superclass
  {@link FieldSerializer} which does not allow to add fields that were formerly
  removed. If this was possible, instances that were serialized before this field
  was added could not longer be properly deserialized. In order to make this contract
  break explicit, you need to create a new instance of this serializer if you want to
  include new fields to a serializer that exclusively serializes annotated fields.
  
  @param clazz The annotation class to be added.
  @return {@code true} if the method call had an effect.