code: def forward(self, item_seq, item_seq_len):
      item_emb, position_embedding = self.embedding_layer(item_seq)
      item_emb = self.LayerNorm(item_emb)
      item_emb = self.dropout(item_emb)
  
      trm_output = self.trm_encoder(
          item_emb, position_embedding, output_all_encoded_layers=True
      )
      output = trm_output[-1]
      output = self.gather_indexes(output, item_seq_len - 1)
      return output
  
file_path: RecBole/recbole/model/sequential_recommender/lightsans.py
imports: import torch
  from torch import nn
  from recbole.model.abstract_recommender import SequentialRecommender
  from recbole.model.loss import BPRLoss
  from recbole.model.layers import LightTransformerEncoder
label_desc: Use image node_id 4 for calling the LightSANs obj's underlying member method code with example usage: obj.forward(item_seq, item_seq_len) and returns: output