[ fromList []
, fromList [ 1 ]
, fromList [ 1 , 7 ]
, fromList [ 1 , 9 ]
, fromList [ 2 ]
, fromList [ 2 , 7 ]
, fromList [ 2 , 7 , 9 ]
, fromList [ 2 , 9 ]
, fromList [ 7 ]
, fromList [ 7 , 9 ]
, fromList [ 9 ]
]