Hi

class OurLLM(CustomLLM):
    context_window: int = 3900
    num_output: int = 256
    model_name: str = "custom"
    dummy_response: str = "My response"

    @property
    def metadata(self) -> LLMMetadata:
        """Get LLM metadata."""
        return LLMMetadata(
            context_window=self.context_window,
            num_output=self.num_output,
            model_name=self.model_name,
        )

    @llm_completion_callback()
    def complete(self, prompt: str, **kwargs: Any) -> CompletionResponse:
        response = requests.post(url, payload) # Just add your url and payload and other needed stuff in here
        return CompletionResponse(text=response.text)

    @llm_completion_callback()
    def stream_complete(
        self, prompt: str, **kwargs: Any
    ) -> CompletionResponseGen:
        response = ""
        for token in self.dummy_response:
            response += token
            yield CompletionResponse(text=response, delta=token)


# define our LLM
Settings.llm = OurLLM()

from llama_index.core import Settings
Settings.llm  = OpenAI(your details) # This will define your llm globally!

# every where your llm is going to be used. 
response = index.as_query_engine.query("your_query")