docs: public void appendSimple(Object... data) {
      if(data.length != meta.size()) {
        throw new AbortException("Invalid number of attributes in 'append'.");
      }
      for(int i = 0; i < data.length; i++) {
        @SuppressWarnings("unchecked")
        final List<Object> col = (List<Object>) columns.get(i);
        col.add(data[i]);
      }
    }