Why set the label tokens the same as the input token

[kaimoxuan123]

System Info

CUDA: 12.1

Information

• The official example scripts
• My own modified scripts

🐛 Describe the bug

Hello, I am learning toxicchat_dataset.py to generate instruction datasets to fine-tune llmam3.1.
https://github.com/meta-llama/llama-recipes/blob/main/src/llama_recipes/datasets/toxicchat_dataset.py#L17

for
ombined_tokens = {
"input_ids": list(prompt_tokens),
"labels": list(prompt_tokens)
}
return dict(combined_tokens, attention_mask=[1]*len(combined_tokens["input_ids"]))
As our task is to predict the next token, why can we offset the label exactlly the same as the input_ids, why don't we offest the input_ids by one token to the right side to get the labels.

Error logs

Read the code to get some experience

Expected behavior

The label is the input_ids shifted to the right by one token