<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_tab(cls):
 """Generate and return the COBS table."""


        if not cls._tabs['dec_cobs']:
            # Compute the COBS table for decoding
            cls._tabs['dec_cobs']['\xff'] = (255, '')
            cls._tabs['dec_cobs'].update(dict((chr(l), (l, '\0'))
                                              for l in range(1, 255)))

            # Compute the COBS table for encoding
            cls._tabs['enc_cobs'] = [(255, '\xff'),
                                     dict((l, chr(l))
                                          for l in range(1, 255)),
                                     ]

        return cls._tabs['dec_cobs'], cls._tabs['enc_cobs']