[feat] Support multimodel mtp

[Jintao-Huang]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces decoder_input propagation through the Multi-Token Prediction (MTP) layers and adds a _get_embeddings helper method to handle sequence rolling and embedding computation. Several critical issues need to be addressed: the forward method signature in patcher.py is missing the decoder_input parameter, which will cause a NameError; the MultiTokenPrediction container requires patching to accept the new argument and avoid a TypeError; the make_viewless_tensor function is used without being imported; and the logic in _get_embeddings should be updated to preserve pre-computed decoder_input values instead of unconditionally overwriting them.

[Jintao-Huang]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces support for multimodal Multi-Token Prediction (MTP) by modifying the GPT model's forward and post-processing logic to handle combined embedding and decoder inputs. It also adds a _get_embeddings method to the MultiTokenPredictionLayer to manage tensor rolling and sequence parallelism. Review feedback suggests addressing a potential IndexError in the _get_embeddings method by rolling along the sequence dimension directly instead of transposing, and improving type safety by adding Union to the imports and updating the embedding argument's type hint.