code: private String callForJsonString(final String host, final int port, final String path,
        List<Pair<String, String>> paramList) throws IOException {
      if (paramList == null) {
        paramList = new ArrayList<>();
      }
  
      @SuppressWarnings("unchecked") final URI uri =
          ExecutorApiClient.buildUri(host, port, path, true);
  
      return this.apiClient.httpPost(uri, paramList);
    }
docs: /*
  Call executor and return raw json string.