docs: public static String getSetKey(ExecutableElement method) {
      StringBuilder result = new StringBuilder();
      AnnotationMirror qualifier = getQualifier(method.getAnnotationMirrors());
      if (qualifier != null) {
        qualifierToString(qualifier, result);
      }
      result.append(SET_PREFIX);
      typeToString(method.getReturnType(), result, '$');
      result.append(">");
      return result.toString();
    }