code: def get_client(site=None):
      
      if 'CITRINATION_API_KEY' not in environ:
          raise ValueError("'CITRINATION_API_KEY' is not set as an environment variable")
      if not site:
          site = environ.get("CITRINATION_SITE", "https://citrination.com")
      return CitrinationClient(environ['CITRINATION_API_KEY'], site)
docs: Get a citrination client