docs: def _token_extensions(self):
          """
          Return a string representation of the OPTIONAL key-value pairs that can be sent with an OAUTHBEARER
          initial request.
          """
          token_provider = self.config['sasl_oauth_token_provider']
  
          # Only run if the #extensions() method is implemented by the clients Token Provider class
          # Builds up a string separated by \x01 via a dict of key value pairs
          if callable(getattr(token_provider, "extensions", None)) and len(token_provider.extensions()) > 0:
              msg = "\x01".join(["{}={}".format(k, v) for k, v in token_provider.extensions().items()])
              return "\x01" + msg
          else:
              return ""