How to use the py4j.protocol function in py4j

# Theoretically, not thread safe, but the worst case scenario is
        # cache miss or double overwrite of the same method...
        if not self._fully_populated:
            if self._auto_field:
                command = proto.DIR_COMMAND_NAME +\
                    proto.DIR_FIELDS_SUBCOMMAND_NAME +\
                    self._target_id + "\n" +\
                    proto.END_COMMAND_PART

                answer = self._gateway_client.send_command(command)
                return_value = get_return_value(
                    answer, self._gateway_client, self._target_id, "__dir__")
                self._field_names.update(return_value.split("\n"))

            command = proto.DIR_COMMAND_NAME +\
                proto.DIR_METHODS_SUBCOMMAND_NAME +\
                self._target_id + "\n" +\
                proto.END_COMMAND_PART

            answer = self._gateway_client.send_command(command)
            return_value = get_return_value(
                answer, self._gateway_client, self._target_id, "__dir__")
            names = return_value.split("\n")
            for name in names:
                if name not in self._methods:
                    self._methods[name] = JavaMember(
                        name, self, self._target_id, self._gateway_client)

            self._fully_populated = True

def new_jvm_view(self, name="custom jvm"):
        """Creates a new JVM view with its own imports. A JVM view ensures
        that the import made in one view does not conflict with the import
        of another view.

        Generally, each Python module should have its own view (to replicate
        Java behavior).

        :param name: Optional name of the jvm view. Does not need to be
            unique, i.e., two distinct views can have the same name
            (internally, they will have a distinct id).

        :rtype: A JVMView instance (same class as the gateway.jvm instance).
        """
        command = proto.JVMVIEW_COMMAND_NAME +\
            proto.JVM_CREATE_VIEW_SUB_COMMAND_NAME +\
            get_command_part(name) +\
            proto.END_COMMAND_PART

        answer = self._gateway_client.send_command(command)
        java_object = get_return_value(answer, self._gateway_client)

        return JVMView(
            gateway_client=self._gateway_client, jvm_name=name,
            jvm_object=java_object)

def __call__(self, *args):
        # TODO Refactor to use a mixin shared by JavaMember and JavaClass
        if self._converters is not None and len(self._converters) > 0:
            (new_args, temp_args) = self._get_args(args)
        else:
            new_args = args
            temp_args = []

        args_command = "".join(
            [get_command_part(arg, self._pool) for arg in new_args])

        command = proto.CONSTRUCTOR_COMMAND_NAME +\
            self._command_header +\
            args_command +\
            proto.END_COMMAND_PART

        answer = self._gateway_client.send_command(command)
        return_value = get_return_value(
            answer, self._gateway_client, None, self._fqn)

        for temp_arg in temp_args:
            temp_arg._detach()

        return return_value

def __getattr__(self, name):
        if name == UserHelpAutoCompletion.KEY:
            return UserHelpAutoCompletion()

        answer = self._gateway_client.send_command(
            proto.REFLECTION_COMMAND_NAME +
            proto.REFL_GET_UNKNOWN_SUB_COMMAND_NAME + name + "\n" + self._id +
            "\n" + proto.END_COMMAND_PART)
        if answer == proto.SUCCESS_PACKAGE:
            return JavaPackage(name, self._gateway_client, jvm_id=self._id)
        elif answer.startswith(proto.SUCCESS_CLASS):
            return JavaClass(
                answer[proto.CLASS_FQN_START:], self._gateway_client)
        else:
            _, error_message = get_error_message(answer)
            message = compute_exception_message(
                "{0} does not exist in the JVM".format(name), error_message)
            raise Py4JError(message)

register_input_converter(ListConverter())

register_output_converter(
    proto.MAP_TYPE, lambda target_id, gateway_client:
    JavaMap(target_id, gateway_client))
register_output_converter(
    proto.LIST_TYPE, lambda target_id, gateway_client:
    JavaList(target_id, gateway_client))
register_output_converter(
    proto.ARRAY_TYPE, lambda target_id, gateway_client:
    JavaArray(target_id, gateway_client))
register_output_converter(
    proto.SET_TYPE, lambda target_id, gateway_client:
    JavaSet(target_id, gateway_client))
register_output_converter(
    proto.ITERATOR_TYPE, lambda target_id, gateway_client:
    JavaIterator(target_id, gateway_client))

def new_array(self, java_class, *dimensions):
        """Creates a Java array of type `java_class` of `dimensions`

        :param java_class: The :class:`JavaClass` instance representing the
            type of the array.

        :param dimensions: A list of dimensions of the array. For example
            `[1,2]` would produce an `array[1][2]`.

        :rtype: A :class:`JavaArray `
            instance.
        """
        if len(dimensions) == 0:
            raise Py4JError("new arrays must have at least one dimension")
        command = proto.ARRAY_COMMAND_NAME +\
            proto.ARRAY_CREATE_SUB_COMMAND_NAME +\
            get_command_part(java_class._fqn)
        for dimension in dimensions:
            command += get_command_part(dimension)
        command += proto.END_COMMAND_PART
        answer = self._gateway_client.send_command(command)
        return get_return_value(answer, self._gateway_client)

while True:
                command = smart_decode(self.input.readline())[:-1]
                if not authenticated:
                    token = self.callback_server_parameters.auth_token
                    # Will raise an exception if auth fails in any way.
                    authenticated = do_client_auth(
                        command, self.input, self.socket, token)
                    continue

                obj_id = smart_decode(self.input.readline())[:-1]
                logger.info(
                    "Received command {0} on object id {1}".
                    format(command, obj_id))
                if obj_id is None or len(obj_id.strip()) == 0:
                    break
                if command == proto.CALL_PROXY_COMMAND_NAME:
                    return_message = self._call_proxy(obj_id, self.input)
                    self.socket.sendall(return_message.encode("utf-8"))
                elif command == proto.GARBAGE_COLLECT_PROXY_COMMAND_NAME:
                    self.input.readline()
                    _garbage_collect_proxy(self.pool, obj_id)
                    self.socket.sendall(
                        proto.SUCCESS_RETURN_MESSAGE.encode("utf-8"))
                else:
                    logger.error("Unknown command {0}".format(command))
                    # We're sending something to prevent blokincg, but at this
                    # point, the protocol is broken.
                    self.socket.sendall(
                        proto.ERROR_RETURN_MESSAGE.encode("utf-8"))
        except Py4JAuthenticationError:
            reset = True
            logger.exception("Could not authenticate connection.")

def __compute_item(self, key):
        new_key = self.__compute_index(key)
        command = proto.ARRAY_COMMAND_NAME +\
            proto.ARRAY_GET_SUB_COMMAND_NAME +\
            self._get_object_id() + "\n"
        command += get_command_part(new_key)
        command += proto.END_COMMAND_PART
        answer = self._gateway_client.send_command(command)
        return get_return_value(answer, self._gateway_client)

def _authenticate_connection(self):
        if self.java_parameters.auth_token:
            cmd = "{0}\n{1}\n".format(
                proto.AUTH_COMMAND_NAME,
                self.java_parameters.auth_token
            )
            answer = self.send_command(cmd)
            error, _ = proto.is_error(answer)
            if error:
                raise Py4JAuthenticationError(
                    "Failed to authenticate with gateway server.")