code: def forward(
      model: Model[InT, OutT], items: InT, is_train: bool
  ) -> Tuple[OutT, Callable]:
      idx = model.attrs["idx"]
      Y_i, backprop_item = model.layers[0](items[idx], is_train)
  
      def backprop(d_output: OutT) -> InT:
          dY_i = backprop_item(d_output[idx])
          return d_output[:idx] + (dY_i,) + d_output[idx + 1 :]
  
      return items[:idx] + (Y_i,) + items[idx + 1 :], backprop
  
imports: from typing import Any, Callable, Optional, Tuple
  from ..config import registry
  from ..model import Model
label_desc: Use image node_id 2 for calling a global function with example usage: forward(model, items, is_train) and returns: unknown,  backprop, unknown