Add chatml chat format

Author: abetlen

llama_cpp/llama_chat_format.py

@@ -91,6 +91,19 @@ def _format_add_colon_space_single(
     return ret
 
 
+def _format_chatml(
+    system_message: str, messages: List[Tuple[str, Optional[str]]], sep: str
+) -> str:
+    """Format the prompt with the chatml style."""
+    ret = "" if system_message == "" else system_message + sep + "\n"
+    for role, message in messages:
+        if message:
+            ret += role + "\n" + message + sep + "\n"
+        else:
+            ret += role + "\n"
+    return ret
+
+
 @dataclasses.dataclass
 class ChatFormatterResponse:
     prompt: str
@@ -290,3 +303,20 @@ def format_open_orca(
     _messages.append((roles[1], None))
     _prompt = _format_add_colon_space_single(system_message, _messages, sep)
     return ChatFormatterResponse(prompt=_prompt, stop=stop_str)
+
+
+@register_chat_format("chatml")
+def format_chatml(
+    messages: List[llama_types.ChatCompletionRequestMessage],
+    **kwargs: Any,
+) -> ChatFormatterResponse:
+    system_template = """<|im_start|>system
+{system_message}"""
+    system_message = _get_system_message(messages)
+    system_message = system_template.format(system_message=system_message)
+    _roles = dict(user="<|im_start|>user", assistant="<|im_start|>assistant")
+    _sep = "<|im_end|>"
+    _messages = _map_roles(messages, _roles)
+    _messages.append((_roles["assistant"], None))
+    _prompt = _format_chatml(system_message, _messages, _sep)
+    return ChatFormatterResponse(prompt=_prompt)