code: private void initializeParser(JsonParser parser) throws IOException {
      if (wrapperKeys.isEmpty()) {
        return;
      }
      boolean failed = true;
      try {
        String match = parser.skipToKey(wrapperKeys);
        Preconditions.checkArgument(
            match != null && parser.getCurrentToken() != JsonToken.END_OBJECT,
            "wrapper key(s) not found: %s",
            wrapperKeys);
        failed = false;
      } finally {
        if (failed) {
          parser.close();
        }
      }
    }
docs: Initialize the parser to skip to wrapped keys (if any).
  
  @param parser JSON parser