class_docstr: Creates a multiprocess vectorized wrapper for multiple environments, distributing each environment to its own
  process, allowing significant speed up when the environment is computationally complex.
  
  For performance reasons, if your environment is not IO bound, the number of environments should not exceed the
  number of logical cores on your CPU.
  
  .. warning::
  
      Only 'forkserver' and 'spawn' start methods are thread-safe,
      which is important when TensorFlow sessions or other non thread-safe
      libraries are used in the parent (see issue #217). However, compared to
      'fork' they incur a small start-up cost and have restrictions on
      global variables. With those methods, users must wrap the code in an
      ``if __name__ == "__main__":`` block.
      For more information, see the multiprocessing documentation.
  
  :param env_fns: ([callable]) A list of functions that will create the environments
      (each callable returns a `Gym.Env` instance when called).
  :param start_method: (str) method used to start the subprocesses.
         Must be one of the methods returned by multiprocessing.get_all_start_methods().
         Defaults to 'forkserver' on available platforms, and 'spawn' otherwise.
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docstr: Return attribute from vectorized environment (see base class).
docstr_tok: ["Return","attribute","from","vectorized","environment","(","see","base","class",")","."]
code: def get_attr(self, attr_name, indices=None):
      """Return attribute from vectorized environment (see base class)."""
      target_remotes = self._get_target_remotes(indices)
      for remote in target_remotes:
          remote.send(("get_attr", attr_name))
      return [remote.recv() for remote in target_remotes]
  
imports: import os
  import multiprocessing
  from collections import OrderedDict
  from typing import Sequence
  import gym
  import numpy
  from stable_baselines.common.vec_env.base_vec_env import VecEnv, CloudpickleWrapper
label_desc: Use image node_id 8 for calling the SubprocVecEnv obj's underlying member method code with example usage: obj.get_attr(attr_name, indices) and returns: unknown