def get_backend_driver(namespace, name, invoke_on_load=False):
    """
    Retrieve a driver (module / class / function) the provided backend.

    :param name: Backend name.
    :type name: ``str``
    """
    # NOTE: We use lazy import because importing from stevedore adds significat import time
    # overhead to other modules which don't need this package (stevedore needs to inspect various
    # entrypoint files on disk for all the installed Python packages which is slow)
    from stevedore.driver import DriverManager

    LOG.debug('Retrieving driver for backend "%s"' % (name))

    try:
        manager = DriverManager(
            namespace=namespace, name=name, invoke_on_load=invoke_on_load
        )
    except RuntimeError:
        message = 'Invalid "%s" backend specified: %s' % (namespace, name)
        LOG.exception(message)
        raise ValueError(message)

    return manager.driver

    Retrieve a driver (module / class / function) the provided backend.

    :param name: Backend name.
    :type name: ``str``
    
st2common/st2common/util/driver_loader.py