def _press_special_key(self, key, down):
        """ Helper method for special keys. 

        Source: http://stackoverflow.com/questions/11045814/emulate-media-key-press-on-mac
        """
        key_code = special_key_translate_table[key]

        ev = NSEvent.otherEventWithType_location_modifierFlags_timestamp_windowNumber_context_subtype_data1_data2_(
                NSSystemDefined, # type
                (0,0), # location
                0xa00 if down else 0xb00, # flags
                0, # timestamp
                0, # window
                0, # ctx
                8, # subtype
                (key_code << 16) | ((0xa if down else 0xb) << 8), # data1
                -1 # data2
            )

        Quartz.CGEventPost(0, ev.Quartz.CGEvent())