title: Multiprocessing with `Pool` throws error on M1 Macbook
body: <p>On my Macbook Pro (Intel, 2020) I can successfully use <code>multiprocessing.Pool</code> like:</p>
  <pre><code>from multiprocessing import Pool
  
  p = Pool(8)
  results = p.map(worker_function, list_of_inputs)
  p.close()
  </code></pre>
  <p>However, if I run the same code on my Macbook Air (M1, 2020), I get a strange error repeated again and again (snippet below):</p>
  <pre class="lang-markdown prettyprint-override"><code>RuntimeError:
          An attempt has been made to start a new process before the
          current process has finished its bootstrapping phase.
  
          This probably means that you are not using fork to start your
          child processes and you have forgotten to use the proper idiom
          in the main module:
  
              if __name__ == '__main__':
                  freeze_support()
                  ...
  
          The &quot;freeze_support()&quot; line can be omitted if the program
          is not going to be frozen to produce an executable.
  </code></pre>