title: When should we call multiprocessing.Pool.join?
body: <p>I am using 'multiprocess.Pool.imap_unordered' as following  </p>
  
  <pre><code>from multiprocessing import Pool
  pool = Pool()
  for mapped_result in pool.imap_unordered(mapping_func, args_iter):
      do some additional processing on mapped_result
  </code></pre>
  
  <p>Do I need to call <code>pool.close</code> or <code>pool.join</code> after the for loop?</p>