def METHOD_NAME(self):
    disk = StorageDevice("testdisk", exists=True)
    disk._partitionable = True
    with patch.object(disk, "_format") as fmt:
        fmt.type = "disklabel"
        self.assertTrue(disk.is_empty)
        PartitionDevice("testpart1", exists=True, parents=[disk])
        self.assertFalse(disk.is_empty)