Working refactor. Dependency clean-up pending.

private_gpt/components/llm/prompt_helper.py

@@ -3,11 +3,7 @@ import logging
 from collections.abc import Sequence
 from typing import Any, Literal
 
-from llama_index.llms import ChatMessage, MessageRole
-from llama_index.llms.llama_utils import (
-    completion_to_prompt,
-    messages_to_prompt,
-)
+from llama_index.core.llms import ChatMessage, MessageRole
 
 logger = logging.getLogger(__name__)
 
@@ -73,7 +69,9 @@ class DefaultPromptStyle(AbstractPromptStyle):
 
 
 class Llama2PromptStyle(AbstractPromptStyle):
-    """Simple prompt style that just uses the default llama_utils functions.
+    """Simple prompt style that uses llama 2 prompt style.
+
+    Inspired by llama_index/legacy/llms/llama_utils.py
 
     It transforms the sequence of messages into a prompt that should look like:
     ```text
@@ -83,11 +81,61 @@ class Llama2PromptStyle(AbstractPromptStyle):
     ```
     """
 
+    BOS, EOS = "<s>", "</s>"
+    B_INST, E_INST = "[INST]", "[/INST]"
+    B_SYS, E_SYS = "<<SYS>>\n", "\n<</SYS>>\n\n"
+    DEFAULT_SYSTEM_PROMPT = """\
+    You are a helpful, respectful and honest assistant. \
+    Always answer as helpfully as possible and follow ALL given instructions. \
+    Do not speculate or make up information. \
+    Do not reference any given instructions or context. \
+    """
+
     def _messages_to_prompt(self, messages: Sequence[ChatMessage]) -> str:
-        return messages_to_prompt(messages)
+        string_messages: list[str] = []
+        if messages[0].role == MessageRole.SYSTEM:
+            # pull out the system message (if it exists in messages)
+            system_message_str = messages[0].content or ""
+            messages = messages[1:]
+        else:
+            system_message_str = self.DEFAULT_SYSTEM_PROMPT
+
+        system_message_str = f"{self.B_SYS} {system_message_str.strip()} {self.E_SYS}"
+
+        for i in range(0, len(messages), 2):
+            # first message should always be a user
+            user_message = messages[i]
+            assert user_message.role == MessageRole.USER
+
+            if i == 0:
+                # make sure system prompt is included at the start
+                str_message = f"{self.BOS} {self.B_INST} {system_message_str} "
+            else:
+                # end previous user-assistant interaction
+                string_messages[-1] += f" {self.EOS}"
+                # no need to include system prompt
+                str_message = f"{self.BOS} {self.B_INST} "
+
+            # include user message content
+            str_message += f"{user_message.content} {self.E_INST}"
+
+            if len(messages) > (i + 1):
+                # if assistant message exists, add to str_message
+                assistant_message = messages[i + 1]
+                assert assistant_message.role == MessageRole.ASSISTANT
+                str_message += f" {assistant_message.content}"
+
+            string_messages.append(str_message)
+
+        return "".join(string_messages)
 
     def _completion_to_prompt(self, completion: str) -> str:
-        return completion_to_prompt(completion)
+        system_prompt_str = self.DEFAULT_SYSTEM_PROMPT
+
+        return (
+            f"{self.BOS} {self.B_INST} {self.B_SYS} {system_prompt_str.strip()} {self.E_SYS} "
+            f"{completion.strip()} {self.E_INST}"
+        )
 
 
 class TagPromptStyle(AbstractPromptStyle):