code: private static Optional<ICondition> asEquals( JsonObject json)
      {
      return
        Optional.of( json)
        .filter( j -> j.containsKey( EQUALS_KEY))
        .map( j -> j.getJsonObject( EQUALS_KEY))
        .map( e -> new Equals( e.getString( PROPERTY_KEY), e.getInt( COUNT_KEY)));
      }
docs: Returns the equals condition represented by the given JSON object or an empty
  value if no such condition is found.