@Override
  public void replaceExprent(Exprent oldExpr, Exprent newExpr) {
    if (oldExpr == instance) {
      instance = newExpr;
    }

    for (int i = 0; i < parameters.size(); i++) {
      if (oldExpr == parameters.get(i)) {
        parameters.set(i, newExpr);
      }
    }
  }
@Override
  public void replaceExprent(Exprent oldExpr, Exprent newExpr)