langchain/libs/partners/prompty/tests/unit_tests/fake_chat_model.py

"""Fake Chat Model wrapper for testing purposes."""
import json
from typing import Any, Dict, List, Optional

from langchain_core.callbacks import (
    AsyncCallbackManagerForLLMRun,
    CallbackManagerForLLMRun,
)
from langchain_core.language_models.chat_models import SimpleChatModel
from langchain_core.messages import AIMessage, BaseMessage
from langchain_core.outputs import ChatGeneration, ChatResult


class FakeEchoPromptChatModel(SimpleChatModel):
    """Fake Chat Model wrapper for testing purposes."""

    def _call(
        self,
        messages: List[BaseMessage],
        stop: Optional[List[str]] = None,
        run_manager: Optional[CallbackManagerForLLMRun] = None,
        **kwargs: Any,
    ) -> str:
        return json.dumps([message.dict() for message in messages])

    async def _agenerate(
        self,
        messages: List[BaseMessage],
        stop: Optional[List[str]] = None,
        run_manager: Optional[AsyncCallbackManagerForLLMRun] = None,
        **kwargs: Any,
    ) -> ChatResult:
        output_str = "fake response 2"
        message = AIMessage(content=output_str)
        generation = ChatGeneration(message=message)
        return ChatResult(generations=[generation])

    @property
    def _llm_type(self) -> str:
        return "fake-echo-prompt-chat-model"

    @property
    def _identifying_params(self) -> Dict[str, Any]:
        return {"key": "fake"}