'Retrieve name of ring files.
If no policy is passed and the server type is object,
the ring names of all storage-policies are retrieved.
:param policy: name or index of storage policy, only applicable
with server_type==object.
:returns: list of ring names.'

def _get_ring_names(self, policy=None):

    if (self.server_type == 'object'):
        ring_names = [p.ring_name for p in POLICIES if ((p.name == policy) or (not policy) or ((policy.isdigit() and (int(policy) == int(p))) or (isinstance(policy, string_types) and (policy in p.aliases))))]
    else:
        ring_names = [self.server_type]
    return ring_names
