async def generate_content_async(
      self, llm_request: LlmRequest, stream: bool = False
  ) -> AsyncGenerator[LlmResponse, None]:
    """Generates one content from the given contents and tools.

    Args:
      llm_request: LlmRequest, the request to send to the LLM.
      stream: bool = False, whether to do streaming call.

    Yields:
      a generator of types.Content.

      For non-streaming call, it will only yield one Content.

      For streaming call, it may yield more than one content, but all yielded
      contents should be treated as one content by merging the
      parts list.
    """
    raise NotImplementedError(
        f'Async generation is not supported for {self.model}.'
    )
    yield  # AsyncGenerator requires a yield statement in function body.
Generates one content from the given contents and tools.

    Args:
      llm_request: LlmRequest, the request to send to the LLM.
      stream: bool = False, whether to do streaming call.

    Yields:
      a generator of types.Content.

      For non-streaming call, it will only yield one Content.

      For streaming call, it may yield more than one content, but all yielded
      contents should be treated as one content by merging the
      parts list.
    
src/google/adk/models/base_llm.py