docstr: Shuts down runners and releases resources.
docstr_tok: ["Shuts","down","runners","and","releases","resources","."]
code: def shutdown(self):
      """
      Shuts down runners and releases resources.
      """
      for runner in self.runners:
          runner.shutdown.remote()
          runner.__ray_terminate__.remote()
  
imports: import os
  import types
  import itertools
  import subprocess
  import ray
  from dmlc_tracker.tracker import get_host_ip
  from zoo.orca.data.utils import ray_partitions_get_data_label, process_spark_xshards
  from zoo.ray import RayContext
  from zoo.orca.learn.mxnet.mxnet_runner import MXNetRunner
  from zoo.orca.learn.mxnet.utils import find_free_port
  from zoo.orca.learn.ray_estimator import Estimator
label_desc: Use image node_id 3 for calling the MXNetEstimator obj's underlying member method code with example usage: obj.shutdown() without return types