docs: def authenticate_with_serviceaccount(reactor, **kw):
      """
      Create an ``IAgent`` which can issue authenticated requests to a
      particular Kubernetes server using a service account token.
  
      :param reactor: The reactor with which to configure the resulting agent.
  
      :param bytes path: The location of the service account directory.  The
          default should work fine for normal use within a container.
  
      :return IAgent: An agent which will authenticate itself to a particular
          Kubernetes server and which will verify that server or refuse to
          interact with it.
      """
      config = KubeConfig.from_service_account(**kw)
      policy = https_policy_from_config(config)
      token = config.user["token"]
      agent = HeaderInjectingAgent(
          _to_inject=Headers({u"authorization": [u"Bearer {}".format(token)]}),
          _agent=Agent(reactor, contextFactory=policy),
      )
      return agent