docs: public static void saveBin(DMatrix A, String fileName)
          throws IOException
      {
          FileOutputStream fileStream = new FileOutputStream(fileName);
          ObjectOutputStream stream = new ObjectOutputStream(fileStream);
  
          try {
              stream.writeObject(A);
              stream.flush();
          } finally {
              // clean up
              try {
                  stream.close();
              } finally {
                  fileStream.close();
              }
          }
  
      }