def planes
import stelliferous@0.0.2.0/tensor_window.bend as TensorWindowimport Base
31# The number of planes before the last two axes; none below rank two.
32def planes(+shape: List<&2,U32>) -> Maybe<&2,U32>:
33 leading(Nat.is_le(2n,List.length(&2,U32,shape)),shape)