code: public static String getSetKey(Type type, Annotation[] annotations, Object subject) {
      Annotation qualifier = extractQualifier(annotations, subject);
      type = boxIfPrimitive(type);
      StringBuilder result = new StringBuilder();
      if (qualifier != null) {
        result.append(qualifier).append("/");
      }
      result.append(SET_PREFIX);
      typeToString(type, result, true);
      result.append(">");
      return result.toString();
    }
docs: Returns a key for {@code type} annotated with {@code annotations},
  wrapped by {@code Set}, reporting failures against {@code subject}.
  
  @param annotations the annotations on a single method, field or parameter.
  This array may contain at most one qualifier annotation.