added llama3 prompt (#1962)

* added llama3 prompt

* more fixes to pass tests; changed type VectorStore -> BasePydanticVectorStore, see https://github.com/run-llama/llama_index/blob/main/CHANGELOG.md#2024-05-14

* fix: new llama3 prompt

---------

Co-authored-by: Javier Martinez <javiermartinezalvarez98@gmail.com>

private_gpt/components/llm/prompt_helper.py

@@ -138,6 +138,73 @@ class Llama2PromptStyle(AbstractPromptStyle):
         )
 
 
+class Llama3PromptStyle(AbstractPromptStyle):
+    r"""Template for Meta's Llama 3.1.
+
+    The format follows this structure:
+    <|begin_of_text|>
+    <|start_header_id|>system<|end_header_id|>
+
+    [System message content]<|eot_id|>
+    <|start_header_id|>user<|end_header_id|>
+
+    [User message content]<|eot_id|>
+    <|start_header_id|>assistant<|end_header_id|>
+
+    [Assistant message content]<|eot_id|>
+    ...
+    (Repeat for each message, including possible 'ipython' role)
+    """
+
+    BOS, EOS = "<|begin_of_text|>", "<|end_of_text|>"
+    B_INST, E_INST = "<|start_header_id|>", "<|end_header_id|>"
+    EOT = "<|eot_id|>"
+    B_SYS, E_SYS = "<|start_header_id|>system<|end_header_id|>", "<|eot_id|>"
+    ASSISTANT_INST = "<|start_header_id|>assistant<|end_header_id|>"
+    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:
+        prompt = self.BOS
+        has_system_message = False
+
+        for i, message in enumerate(messages):
+            if not message or message.content is None:
+                continue
+            if message.role == MessageRole.SYSTEM:
+                prompt += f"{self.B_SYS}\n\n{message.content.strip()}{self.E_SYS}"
+                has_system_message = True
+            else:
+                role_header = f"{self.B_INST}{message.role.value}{self.E_INST}"
+                prompt += f"{role_header}\n\n{message.content.strip()}{self.EOT}"
+
+            # Add assistant header if the last message is not from the assistant
+            if i == len(messages) - 1 and message.role != MessageRole.ASSISTANT:
+                prompt += f"{self.ASSISTANT_INST}\n\n"
+
+        # Add default system prompt if no system message was provided
+        if not has_system_message:
+            prompt = (
+                f"{self.BOS}{self.B_SYS}\n\n{self.DEFAULT_SYSTEM_PROMPT}{self.E_SYS}"
+                + prompt[len(self.BOS) :]
+            )
+
+        # TODO: Implement tool handling logic
+
+        return prompt
+
+    def _completion_to_prompt(self, completion: str) -> str:
+        return (
+            f"{self.BOS}{self.B_SYS}\n\n{self.DEFAULT_SYSTEM_PROMPT}{self.E_SYS}"
+            f"{self.B_INST}user{self.E_INST}\n\n{completion.strip()}{self.EOT}"
+            f"{self.ASSISTANT_INST}\n\n"
+        )
+
+
 class TagPromptStyle(AbstractPromptStyle):
     """Tag prompt style (used by Vigogne) that uses the prompt style `<|ROLE|>`.
 
@@ -219,7 +286,8 @@ class ChatMLPromptStyle(AbstractPromptStyle):
 
 
 def get_prompt_style(
-    prompt_style: Literal["default", "llama2", "tag", "mistral", "chatml"] | None
+    prompt_style: Literal["default", "llama2", "llama3", "tag", "mistral", "chatml"]
+    | None
 ) -> AbstractPromptStyle:
     """Get the prompt style to use from the given string.
 
@@ -230,6 +298,8 @@ def get_prompt_style(
         return DefaultPromptStyle()
     elif prompt_style == "llama2":
         return Llama2PromptStyle()
+    elif prompt_style == "llama3":
+        return Llama3PromptStyle()
     elif prompt_style == "tag":
         return TagPromptStyle()
     elif prompt_style == "mistral":