About formatting

[alvarobartt]

Description

Currently distilabel handles the formatting as part of the class Prompt that expects a system_prompt and a formatted_prompt, since it was the most suitable solution for the initial approach i.e. UltraFeedback, as we have a one-turn interaction where we have a system_prompt and a default formatting suited for a given task, in this case UltraFeedback. The Prompt class also contains a method named format_as that contains some standard formats, to go from system_prompt and formatted_prompt to the formatting expected by a given model, where the formatted_prompt is the first user message within a chat-like application, and the assistant follow-up is the completion to it i.e. the expected output.

But this approach is a bit weak under some scenarios, as multi-turn is not supported, and the formatting may get complex if i.e. there's not a system_prompt, the formatted_output is a sequence of messages, etc.

So on, IMHO we should refactor that to support only the following scenarios:

• Pre-defined tasks such as UltraFeedbackTask produce a Prompt following OpenAI formatting, meaning a one-turn only; and the format conversion is handled within the Prompt (similarly to what's being done with the Chat class in Add ChatTask for multi-turn and follow-up generation #203)
• Some helper functions can be provided to easily go from one formatting to another i.e. from Zephyr to OpenAI

This way we end up with a more custom experience, as the task is the one that decides how the formatting happens and the standard output is formatted as OpenAI specifies. Meaning that the input for a given generate_prompt function within a Task could handle both multi-turn and one-turn prompts if needed.