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As discussed on Discord, the decision has been made to remove the system prompts by default, to better segregate the API and the UI usages. A concurrent PR (#1353) is enabling the dynamic setting of a system prompt in the UI. Therefore, if UI users want to use a custom system prompt, they can specify one directly in the UI. If the API users want to use a custom prompt, they can pass it directly into their messages that they are passing to the API. In the highlight of the two use case above, it becomes clear that default system_prompt does not need to exist.
140 lines
4.9 KiB
Python
140 lines
4.9 KiB
Python
import abc
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import logging
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from collections.abc import Sequence
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from typing import Any, Literal
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from llama_index.llms import ChatMessage, MessageRole
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from llama_index.llms.llama_utils import (
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completion_to_prompt,
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messages_to_prompt,
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)
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logger = logging.getLogger(__name__)
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class AbstractPromptStyle(abc.ABC):
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"""Abstract class for prompt styles.
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This class is used to format a series of messages into a prompt that can be
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understood by the models. A series of messages represents the interaction(s)
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between a user and an assistant. This series of messages can be considered as a
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session between a user X and an assistant Y.This session holds, through the
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messages, the state of the conversation. This session, to be understood by the
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model, needs to be formatted into a prompt (i.e. a string that the models
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can understand). Prompts can be formatted in different ways,
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depending on the model.
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The implementations of this class represent the different ways to format a
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series of messages into a prompt.
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"""
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def __init__(self, *args: Any, **kwargs: Any) -> None:
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logger.debug("Initializing prompt_style=%s", self.__class__.__name__)
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@abc.abstractmethod
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def _messages_to_prompt(self, messages: Sequence[ChatMessage]) -> str:
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pass
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@abc.abstractmethod
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def _completion_to_prompt(self, completion: str) -> str:
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pass
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def messages_to_prompt(self, messages: Sequence[ChatMessage]) -> str:
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prompt = self._messages_to_prompt(messages)
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logger.debug("Got for messages='%s' the prompt='%s'", messages, prompt)
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return prompt
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def completion_to_prompt(self, completion: str) -> str:
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prompt = self._completion_to_prompt(completion)
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logger.debug("Got for completion='%s' the prompt='%s'", completion, prompt)
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return prompt
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class DefaultPromptStyle(AbstractPromptStyle):
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"""Default prompt style that uses the defaults from llama_utils.
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It basically passes None to the LLM, indicating it should use
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the default functions.
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"""
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def __init__(self, *args: Any, **kwargs: Any) -> None:
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super().__init__(*args, **kwargs)
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# Hacky way to override the functions
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# Override the functions to be None, and pass None to the LLM.
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self.messages_to_prompt = None # type: ignore[method-assign, assignment]
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self.completion_to_prompt = None # type: ignore[method-assign, assignment]
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def _messages_to_prompt(self, messages: Sequence[ChatMessage]) -> str:
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return ""
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def _completion_to_prompt(self, completion: str) -> str:
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return ""
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class Llama2PromptStyle(AbstractPromptStyle):
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"""Simple prompt style that just uses the default llama_utils functions.
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It transforms the sequence of messages into a prompt that should look like:
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```text
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<s> [INST] <<SYS>> your system prompt here. <</SYS>>
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user message here [/INST] assistant (model) response here </s>
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```
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"""
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def _messages_to_prompt(self, messages: Sequence[ChatMessage]) -> str:
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return messages_to_prompt(messages)
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def _completion_to_prompt(self, completion: str) -> str:
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return completion_to_prompt(completion)
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class TagPromptStyle(AbstractPromptStyle):
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"""Tag prompt style (used by Vigogne) that uses the prompt style `<|ROLE|>`.
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It transforms the sequence of messages into a prompt that should look like:
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```text
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<|system|>: your system prompt here.
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<|user|>: user message here
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(possibly with context and question)
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<|assistant|>: assistant (model) response here.
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```
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FIXME: should we add surrounding `<s>` and `</s>` tags, like in llama2?
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"""
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def _messages_to_prompt(self, messages: Sequence[ChatMessage]) -> str:
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"""Format message to prompt with `<|ROLE|>: MSG` style."""
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prompt = ""
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for message in messages:
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role = message.role
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content = message.content or ""
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message_from_user = f"<|{role.lower()}|>: {content.strip()}"
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message_from_user += "\n"
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prompt += message_from_user
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# we are missing the last <|assistant|> tag that will trigger a completion
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prompt += "<|assistant|>: "
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return prompt
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def _completion_to_prompt(self, completion: str) -> str:
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return self._messages_to_prompt(
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[ChatMessage(content=completion, role=MessageRole.USER)]
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)
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def get_prompt_style(
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prompt_style: Literal["default", "llama2", "tag"] | None
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) -> AbstractPromptStyle:
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"""Get the prompt style to use from the given string.
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:param prompt_style: The prompt style to use.
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:return: The prompt style to use.
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"""
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if prompt_style is None or prompt_style == "default":
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return DefaultPromptStyle()
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elif prompt_style == "llama2":
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return Llama2PromptStyle()
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elif prompt_style == "tag":
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return TagPromptStyle()
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raise ValueError(f"Unknown prompt_style='{prompt_style}'")
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