code: def forward(
      model: Model[List[InT], List[OutT]], Xs: List[InT], is_train: bool
  ) -> Tuple[List[OutT], Callable[[List[OutT]], List[InT]]]:
      layer = model.layers[0]
      Ys = []
      callbacks = []
      for X in Xs:
          Y, get_dX = layer(X, is_train)
          Ys.append(Y)
          callbacks.append(get_dX)
  
      def backprop_map_list(dYs: List[OutT]) -> List[InT]:
          return [callback(dY) for callback, dY in zip(callbacks, dYs)]
  
      return Ys, backprop_map_list
  
imports: from typing import Callable, List, Optional, Tuple, TypeVar
  from ..model import Model
label_desc: Use image node_id 2 for calling a global function with example usage: forward(model, Xs, is_train) and returns: Ys,  backprop_map_list, unknown