def __virtual__():
    if 'boto_rds.exists' in __salt__:
        return 'boto_rds'
    return(False, __salt__.missing_fun_string('boto_rds.exists'))
Can pass dotted path to load arbirary backend
dataset/ETHPy150Open saltstack/salt/salt/states/boto_rds.py/__virtual__--crossover with--dataset/ETHPy150Open mathcamp/pypicloud/tests/test_access_backends.py/TestBaseBackend.test_load_arbitrary_backend