Can not invoke custom imported AWS Bedrock model

[shrijayan]

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Example Code

from langchain_aws import ChatBedrock
 
llm = ChatBedrock(
    model_id="<ARN>",
    model_kwargs=dict(temperature=0),
    region_name="<region>",
    provider="imported-model"
)
 
messages = [
    (
        "system",
        "You are a helpful assistant that translates English to French. Translate the user sentence.",
    ),
    ("human", "I love programming."),
]
# response = llm.predict(text="Translate to French: I love programming.")
# llm.invoke(messages)
# llm.invoke(message="Hi")

Description

Error while trying to use custom imported models in bedrock

Traceback (most recent call last):
  File "src/llm-bedrock.py", line 18, in <module>
    llm.invoke(messages)
  File ".venv/lib/python3.11/site-packages/langchain_core/language_models/chat_models.py", line 286, in invoke
    self.generate_prompt(
  File ".venv/lib/python3.11/site-packages/langchain_core/language_models/chat_models.py", line 786, in generate_prompt
    return self.generate(prompt_messages, stop=stop, callbacks=callbacks, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.11/site-packages/langchain_core/language_models/chat_models.py", line 643, in generate
    raise e
  File ".venv/lib/python3.11/site-packages/langchain_core/language_models/chat_models.py", line 633, in generate
    self._generate_with_cache(
  File ".venv/lib/python3.11/site-packages/langchain_core/language_models/chat_models.py", line 851, in _generate_with_cache
    result = self._generate(
             ^^^^^^^^^^^^^^^
  File ".venv/lib/python3.11/site-packages/langchain_aws/chat_models/bedrock.py", line 563, in _generate
    prompt = ChatPromptAdapter.convert_messages_to_prompt(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.11/site-packages/langchain_aws/chat_models/bedrock.py", line 362, in convert_messages_to_prompt
    raise NotImplementedError(
NotImplementedError: Provider imported-model model does not support chat.

System Info

langchain-aws==0.2.9
langchain-core==0.3.22
langsmith==0.1.147

python3.11