str: database system group (defaults to
        :attr:`db_user <tmdeploy.config.AnsibleHostVariableSection.db_user>`)

def db_group(self):
        '''str: database system group (defaults to
        :attr:`db_user <tmdeploy.config.AnsibleHostVariableSection.db_user>`)
        '''
        if self._db_group is None:
            self._db_group = self.db_user
        return self._db_group