message: unregistering all data frames on connection close so we dont leak python references
diff: @@ -400,6 +400,12 @@ struct DuckDBPyConnection {
  return this;
  }
  + ~DuckDBPyConnection() {
  + for (auto& element : registered_dfs) {
  + unregister_df(element.first);
  + }
  + }
  +
  DuckDBPyConnection *execute(string query, py::object params = py::list(), bool many = false) {
  if (!connection) {
  throw runtime_error("connection closed");
  