code: public AnnotatedTypeBuilder<X> addToField(AnnotatedField<? super X> field, Annotation annotation) {
         return addToField(field.getJavaMember(), annotation);
     }
docs: Add an annotation to the specified field. If the field is not already
  present, it will be added.
  
  @param field      the field to add the annotation to
  @param annotation the annotation to add
  @throws IllegalArgumentException if the annotation is null