code: private static Optional<ICondition> asAnyOf( JsonObject json)
      {
      return
        json.containsKey( ANY_OF_KEY)
        ? Optional.of( new AnyOf( toConditions( json.getJsonArray( ANY_OF_KEY))))
        : Optional.empty();
      }
docs: Returns the AnyOf condition represented by the given JSON object or an empty
  value if no such condition is found.