message: For NOT operator, print it inside parentheses
diff: @@ -57,7 +57,15 @@ public:
  child_list += ")";
  return "(" + in_child + op_type + child_list + ")";
  }
  - case ExpressionType::OPERATOR_NOT:
  + case ExpressionType::OPERATOR_NOT: {
  + string result = "(";
  + result += ExpressionTypeToString(entry.type);
  + result += " ";
  + result += StringUtil::Join(entry.children, entry.children.size(), ", ",
  + [](const unique_ptr<BASE> &child) { return child->ToString(); });
  + result += ")";
  + return result;
  + }
  case ExpressionType::GROUPING_FUNCTION:
  case ExpressionType::OPERATOR_COALESCE: {
  string result = ExpressionTypeToString(entry.type);
  