module type BT  = BTree
module type BT  = MultiCore.BTree
module type BT  = Std.MultiCore.BTree
module type BT  = ((BTree)[@attr ])
module type BT  = ((MultiCore.BTree)[@attr ][@attr2 ])
module type BT  = ((Std.MultiCore.BTree)[@attr ][@attr2 ][@attr3 ])
module type list  = list
module type t  = s