guavasupport/src/main/java/com/streamsets/pipeline/lib/io/fileref/AbstractWrapperStream.java
@Override
  public int read(byte[] b, int offset, int len) throws IOException {
    checkState(InputStream.class);
    return  ((InputStream)stream).read(b, offset, len);
  }
@Override
  public int read(byte[] b, int offset, int len) throws IOException {
    checkState(InputStream.class);
    return  ((InputStream)stream).read(b, offset, len);
  }
InputStream