docs: def begin_transaction(self):
          """Starts a transaction by suspending auto-commit mode."""
          self.ensure_connected()
          self._transaction_nesting_level += 1
          if self._transaction_nesting_level == 1:
              self._driver.begin_transaction()
          elif self._nest_transactions_with_savepoints:
              self.create_savepoint(self._get_nested_transaction_savepoint_name())