This notebook goes over how to use Langchain with YandexGPT chat model. To use, you should have the yandexcloud python package installed. 
%pip install --upgrade --quiet  yandexcloud
First, you should create service account with the ai.languageModels.user role. Next, you have two authentication options:
  • IAM token. You can specify the token in a constructor parameter iam_token or in an environment variable YC_IAM_TOKEN.
  • API key You can specify the key in a constructor parameter api_key or in an environment variable YC_API_KEY.
To specify the model you can use model_uri parameter, see the documentation for more details. By default, the latest version of yandexgpt-lite is used from the folder specified in the parameter folder_id or YC_FOLDER_ID environment variable. 
from langchain_community.chat_models import ChatYandexGPT
from langchain_core.messages import HumanMessage, SystemMessage

chat_model = ChatYandexGPT()

answer = chat_model.invoke(
    [
        SystemMessage(
            content="You are a helpful assistant that translates English to French."
        ),
        HumanMessage(content="I love programming."),
    ]
)
answer

AIMessage(content='Je adore le programmement.')