docs: void setMemo(String production, int position, int line, final MemoEntry stackElement) {
  	Map<String, MemoEntry> map = memo.get(position);
  	if (map == null) {
  	    map = new HashMap<String, MemoEntry>();
  	    memo.put(position, map);
  	    map.put(production, stackElement);
  	} else {
  	    if (map.containsKey(production)) {
  		throw new RuntimeException("We should not set a memo twice. Modifying is needed afterwards.");
  	    }
  	    map.put(production, stackElement);
  	}
      }