code: private static AnnotationValue assertAnnotationValue( Declaration element, String annotationName, String valueName,
                                                            boolean defaultIsNull )
      {
          AnnotationInstance ann = getAnnotation( element, annotationName );
          
          if ( ann == null )
          {
              return null;
          }
          else
          {
              return getAnnotationValue( ann, valueName, defaultIsNull );
          }
      }
docs: If the given annotation exists, assert that the given member is not null</code>, and return it; otherwise,
  if the given annotation does not exist, return null</code>.