How to use the ocpp.messages.unpack function in ocpp

def test_unpack_without_message_type_id_in_json():
    """
    OCPP must contain the MessageTypeID as first element of the message.
    This test validates if correct exception is raised when this is not
    the case
    """
    with pytest.raises(ProtocolError):
        unpack(json.dumps([]))

def test_unpack_with_invalid_json():
    """
    Test that correct exception is raised when unpack is called with invalid
    JSON.
    """
    with pytest.raises(FormatViolationError):
        unpack(b'\x01')

def test_unpack_without_jsonified_list():
    """
    OCPP messages are JSONified lists. This test make sure that the correct
    exception is raised when input is not a JSONified list.
    """
    with pytest.raises(ProtocolError):
        unpack(json.dumps('3'))

def test_unpack_with_invalid_message_type_id_in_json():
    """
    OCPP messages only have 3 valid values for MessageTypeID, that is the first
    element of the OCPP message. This test validates that correct exception is
    raised when this value is invalid.
    """
    with pytest.raises(PropertyConstraintViolationError):
        unpack(json.dumps([5, 1]))

async def route_message(self, raw_msg):
        """
        Route a message received from a CP.

        If the message is a of type Call the corresponding hooks are executed.
        If the message is of type CallResult or CallError the message is passed
        to the call() function via the response_queue.
        """
        try:
            msg = unpack(raw_msg)
        except OCPPError as e:
            LOGGER.exception("Unable to parse message: '%s', it doesn't seem "
                             "to be valid OCPP: %s", raw_msg, e)
            return

        if msg.message_type_id == MessageType.Call:
            await self._handle_call(msg)
        elif msg.message_type_id in \
                [MessageType.CallResult, MessageType.CallError]:
            self._response_queue.put_nowait(msg)