code: def resolve_generator(
      generation_model: str, llm_api_key: Optional[str] = None
  ) -> Optional[Any]:
      """
      Resolves the generator to use for the given generation model.
      :param generation_model: The generation model to use.
      :param llm_api_key: The API key to use for the language model.
      """
      generator = None
      for resolver_clazz in _GeneratorResolver.get_resolvers():
          resolver = resolver_clazz()
          generator = resolver.resolve(generation_model, llm_api_key)
          if generator:
              break
      if not generator:
          raise ValueError(
              f"Could not resolve LLM generator for the given model {generation_model}"
          )
      return generator
  
imports: import re
  from abc import ABC, abstractmethod
  from typing import Optional, Any
  from huggingface_hub import HfApi
  from haystack import Pipeline
  from haystack.components.builders.answer_builder import AnswerBuilder
  from haystack.components.builders.prompt_builder import PromptBuilder
  from haystack.components.embedders import SentenceTransformersTextEmbedder
  from haystack.components.generators import OpenAIGenerator, HuggingFaceTGIGenerator
  from haystack.components.retrievers.in_memory import InMemoryEmbeddingRetriever
  from haystack.dataclasses import Answer
  from haystack.document_stores.types import DocumentStore
  from haystack.document_stores.in_memory import InMemoryDocumentStore
label_desc: Use image node_id 4 for calling a global function with example usage: resolve_generator(generation_model, llm_api_key) and returns: generator