a `config` is provided or automatically loaded.

        Example:

        ```python
        >>> from transformers import MusicgenForConditionalGeneration

        >>> # initialize a musicgen model from a t5 text encoder, encodec audio encoder, and musicgen decoder
        >>> model = MusicgenForConditionalGeneration.from_sub_models_pretrained(
        ...     text_encoder_pretrained_model_name_or_path="t5-base",
        ...     audio_encoder_pretrained_model_name_or_path="facebook/encodec_24khz",
        ...     decoder_pretrained_model_name_or_path="facebook/musicgen-small",
        ... )
        >>> # saving model after fine-tuning
        >>> model.save_pretrained("./musicgen-ft")
        >>> # load fine-tuned model
        >>> model = MusicgenForConditionalGeneration.from_pretrained("./musicgen-ft")
        ```c