docs: public InputStream load(String folder, String file) throws IOException {
        if (content.containsKey(folder+"/"+file))
          return new ByteArrayInputStream(content.get(folder+"/"+file));
        else {
          File f = new File(Utilities.path(path, folder, file));
          if (f.exists())
            return new FileInputStream(f);
          throw new IOException("Unable to find the file "+folder+"/"+file+" in the package "+name());
        }
      }