def source_index
import bendtorch-core@0.1.0.0/src/autograd/reduce_to_fold_PROOF.bend as ReduceToFoldPROOFimport Base
import bendtorch-core@0.1.0.0/src/shape/core.bend as Shape
import bendtorch-core@0.1.0.0/src/autograd/reduce_fold.bend as ReduceFold
101def source_index(+plan: Shape.BroadcastPlan, +position: Nat) -> U32:
102 U32.from_nat(ReduceFold.contribution_offset(plan, position))