When the transaction is finished, why the connection is not explicitly closed?

[liqueur]

the transaction wrapper in database.py

def __exit__(self, error_type, error_value, traceback):
    """End a transaction by committing or rolling back."""
    if error_type is None:
        try:
            self.commit()
        except:
            with safe_reraise():
                self.rollback()
    else:
        self.rollback()