@Override
  public SeekableInputStream newStream() throws IOException {
    // Note: this doesn't maintain proper newStream semantics (if any). 
    //       We could either clone this instead or enforce that this is only called once.
    return this;
  }
The Parquet InputFile implementation that allows the reader to
read the footer from cache without being aware of the latter.
This implements both InputFile and the InputStream that the reader gets from InputFile.
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/vector/ParquetFooterInputFromCache.java