'Get the members of a volume group.
:param array: the array serial number
:param group_name: the storage group name
:returns: list -- member_device_ids'

def _get_members_of_volume_group(self, array, group_name):

    member_device_ids = self.rest.get_volumes_in_storage_group(array, group_name)
    if (not member_device_ids):
        LOG.info('No    member    volumes    found    in    %(group_id)s', {'group_id': group_name})
    return member_device_ids
