code: def pull(self, keys):
      return [self.weights[key] for key in keys]
  
file_path: BigDL/python/orca/example/ray_on_spark/parameter_server/async_parameter_server.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import argparse
  import os
  import time
  import ray
  from model import SimpleCNN, download_mnist_retry
  from bigdl.orca import init_orca_context, stop_orca_context
  from bigdl.orca import OrcaContext
label_desc: Use image node_id 3 for calling the ParameterServer obj's underlying member method code with example usage: obj.pull(keys) and returns: unknown