code: def shell(cmd):
      "Simple wrapper for calling docker, returning None on error and the output on success"
      try:
          return subprocess.check_output(['docker'] + cmd, stderr=subprocess.STDOUT).decode('utf8').strip()
      except subprocess.CalledProcessError:
          return Nonf shell(cmd):
      "Simple wrapper for calling docker, returning None on error and the output on success"
      try:
          return subprocess.check_output(['docker'] + cmd, stderr=subprocess.STDOUT).decode('utf8').strip()
      except subprocess.CalledProcessError:
          return None
docs: Simple wrapper for calling docker, returning None on error and the output on success