@Override
      public void begin(FanOutOneBlockAsyncDFSOutput output) {
        try {
          beginFileLeaseMethod.invoke(output.getClient(), output.getDummyStream().getFileId(),
            output.getDummyStream());
        } catch (IllegalAccessException | InvocationTargetException e) {
          throw new RuntimeException(e);
        }
      }
Helper class for implementing {@link FanOutOneBlockAsyncDFSOutput}.
hbase-asyncfs/src/main/java/org/apache/hadoop/hbase/io/asyncfs/FanOutOneBlockAsyncDFSOutputHelper.java