code: def to_cpu(b:ItemsList):
      "Recursively map lists of tensors in `b ` to the cpu."
      if is_listy(b): return [to_cpu(o) for o in b]
      return b.cpu() if isinstance(b,Tensor) else f to_cpu(b:ItemsList):
      "Recursively map lists of tensors in `b ` to the cpu."
      if is_listy(b): return [to_cpu(o) for o in b]
      return b.cpu() if isinstance(b,Tensor) else b
docs: Recursively map lists of tensors in `b ` to the cpu.