Reading Client protocol property causes infinite recursion loop

[asikeero]

Bug Description

Accessing the field Client.protocol causes infinite recursion, since there is a bug in how that property is defined. The bug is on this line. The function should return self._protocol and not self.protocol as the latter is a recursive definition.
This is the property.

    @property
    def protocol(self) -> MQTTProtocolVersion:
        """
        Protocol version used (MQTT v3, MQTT v3.11, MQTTv5)

        This property is read-only.
        """
        return self.protocol