code: def test_bert4rec(self) -> None:
      # input tensor
      # [2, 4],
      # [3, 4, 5],
      input_kjt = KeyedJaggedTensor.from_lengths_sync(
          keys=["item"],
          values=torch.tensor([2, 4, 3, 4, 5]),
          lengths=torch.tensor([2, 3]),
      )
      device = (
          torch.device("cuda")
          if torch.cuda.is_available()
          else torch.device("cpu")
      )
      input_kjt = input_kjt.to(device)
      bert4rec = BERT4Rec(
          vocab_size=6,
          max_len=3,
          emb_dim=4,
          nhead=4,
          num_layers=4,
          device=device,
      )
      logits = bert4rec(input_kjt)
      assert logits.size() == torch.Size(
          [input_kjt.stride(), bert4rec.max_len, bert4rec.vocab_size]
      )
  
imports: import unittest
  import torch
  from torchrec.sparse.jagged_tensor import KeyedJaggedTensor
  from ..bert4rec import BERT4Rec
label_desc: Use image node_id 1 for calling the BERT4RecTest obj's underlying member method code with example usage: obj.test_bert4rec() without return types