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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _read_mptcp_prio(self, bits, size):
 """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) """

        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