code: def validate_environment(api_key):
      if api_key is None:
          raise ValueError(
              "Missing Anthropic API Key - A call is being made to anthropic but no key is set either in the environment variables or via params"
          )
      headers = {
          "accept": "application/json",
          "anthropic-version": "2023-06-01",
          "content-type": "application/json",
          "x-api-key": api_key,
      }
      return headers
  
imports: import os, types
  import json
  from enum import Enum
  import requests
  import time
  from typing import Callable, Optional
  from litellm.utils import ModelResponse, Usage
  import litellm
  from .prompt_templates.factory import prompt_factory, custom_prompt
  import httpx
label_desc: Use image node_id 1 for calling a global function with example usage: validate_environment(api_key) and returns: headers