code: public void readToken(String parentFieldName, JsonToken expectedToken)
      throws IOException {
      JsonToken currentToken = jsonParser.nextToken();
      if (currentToken != expectedToken) {
        throw new IOException("Expected a " + expectedToken.toString() +
          " token when reading the value of the field: " +
          parentFieldName +
          " but found a " +
          currentToken.toString() + " token");
      }
    }
docs: This is a helper method that reads a JSON token using a JsonParser
  instance, and throws an exception if the next token is not the same as
  the token we expect.
  
  @param parentFieldName The name of the field
  @param expectedToken The expected token
  @throws IOException