code: def _read_mptcp_prio(self, bits, size):
          
          temp = self._read_unpack(1) if size else None
  
          data = dict(
              subtype='MP_PRIO',
              prio=dict(
                  res=b'\x00' * 3,
                  backup=True if int(bits[3]) else False,
                  addrid=temp,
              ),
          )
  
          return data
docs: Read Change Subflow Priority option.
  
          Positional arguments:
              * bits - str, 4-bit data
              * size - int, length of option
  
          Returns:
              * dict -- extracted Change Subflow Priority (MP_PRIO) option
  
          Structure of MP_PRIO [RFC 6824]:
                                    1                   2                   3
                0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
              +---------------+---------------+-------+-----+-+--------------+
              |     Kind      |     Length    |Subtype|     |B| AddrID (opt) |
              +---------------+---------------+-------+-----+-+--------------+
  
              Octets      Bits        Name                    Description
                0           0     tcp.opt.kind            Kind (30)
                1           8     tcp.opt.length          Length (3/4)
                2          16     tcp.opt.mp.subtype      Subtype (5)
                2          23     tcp.opt.mp.prio.backup  Backup Path (B)
                3          24     tcp.opt.mp.prio.addrid  Address ID (optional)