docs: def s2i_frameid(x):
      """ Get pnio frame ID from a representation name
  
      Performs a reverse look-up in PNIO_FRAME_IDS dictionary
  
      :param x: a value of PNIO_FRAME_IDS dict
      :returns: integer
      """
      try:
          return {
              "RT_CLASS_3": 0x0100,
              "RT_CLASS_1": 0x8000,
              "RT_CLASS_UDP": 0xC000,
              "FragmentationFrameID": 0xFF80,
          }[x]
      except KeyError:
          pass
      try:
          return next(key for key, value in six.iteritems(PNIO_FRAME_IDS)
                      if value == x)
      except StopIteration:
          pass
      return x