code: @Override
      public Map<String, String[]> getSimpleMaster(String[] masterLabels,
                                                   int joinColumnNo,
                                                   String path,
                                                   String separator) throws IOException, URISyntaxException {
          Map<String, String[]> m = new HashMap<String, String[]>();
  
          URI uri = new URI(path);
          String key = uri.getPath().substring(1);
          S3Object s3Object = s3.getObject(uri.getHost(), key);
  
          BufferedReader br =
                  new BufferedReader(new InputStreamReader(s3Object.getObjectContent(), "UTF-8"));
  
          String line;
          while ((line = br.readLine()) != null) {
              String[] strings = StringUtil.split(line, separator, false);
              if (masterLabels.length != strings.length) {
                  continue;
              }
  
              String joinData = strings[joinColumnNo];
              String[] data = new String[strings.length];
              for (int i = 0; i < strings.length; i++) {
                  data[i] = strings[i];
              }
  
              m.put(joinData, data);
          }
          br.close();
  
          return m;
      }
docs: {@inheritDoc}