auto it = buffer_to_size.find(length.getInputHandle());
  if (it == buffer_to_size.end()) {
    length.emitOpError("found tf.TensorListLength on unknown TensorList.");
    return failure();
  }
  OpBuilder builder(length);
  if (it->getSecond().fixed) {
    auto dim = cutil::CreateScalarConst(
        mlir::cast<RankedTensorType>(length.getInputHandle().getType())
            .getDimSize(0),

        parent = identity.getInput();
      } else if (auto set_item =
                     parent.getDefiningOp<TF::TensorListSetItemOp>()) {
        parent = set_item.getInputHandle();
      } else {
        break;
      }
    }
    if (auto block_arg = parent.dyn_cast<mlir::BlockArgument>()) {
      return block_arg.getArgNumber();
    }

    // Checks that the input is created by TensorListFromTensorOp and the input
    // is only used by TensorListGetItemOp.
    auto tensor_list_from_tensor_op = dyn_cast_or_null<TensorListFromTensorOp>(
        op.getInputHandle().getDefiningOp());
    if (!tensor_list_from_tensor_op ||
        llvm::any_of(
            tensor_list_from_tensor_op->getUsers(),
            [](Operation *user) { return !isa<TensorListGetItemOp>(user); })) {