How to use the stone.backends.obj_c_helpers.fmt_func_call function in stone

return_type='nullable NSDictionary  *',
                class_func=True):
            func_call = fmt_func_call(
                caller=fmt_serial_class(data_type_name),
                callee='serialize',
                args=fmt_func_args([('instance', 'instance')]))
            self.emit('return {};'.format(func_call))
        self.emit()

        with self.block_func(
                func='deserialize',
                args=fmt_func_args_declaration([('dict', 'NSDictionary  *')]),
                return_type='id',
                class_func=True):
            self.emit('return {};'.format(
                fmt_func_call(
                    caller=fmt_serial_class(data_type_name),
                    callee='deserialize',
                    args=fmt_func_args([('dict', 'dict')]))))
        self.emit()

def _generate_serializable_funcs(self, data_type_name):
        """Emits the two struct/union functions that implement the Serializable protocol."""
        with self.block_func(
                func='serialize',
                args=fmt_func_args_declaration([('instance', 'id')]),
                return_type='nullable NSDictionary  *',
                class_func=True):
            func_call = fmt_func_call(
                caller=fmt_serial_class(data_type_name),
                callee='serialize',
                args=fmt_func_args([('instance', 'instance')]))
            self.emit('return {};'.format(func_call))
        self.emit()

        with self.block_func(
                func='deserialize',
                args=fmt_func_args_declaration([('dict', 'NSDictionary  *')]),
                return_type='id',
                class_func=True):
            self.emit('return {};'.format(
                fmt_func_call(
                    caller=fmt_serial_class(data_type_name),
                    callee='deserialize',
                    args=fmt_func_args([('dict', 'dict')]))))

if is_primitive_type(data_type):
                            deserialize_call = '{} ?: {}'.format(
                                input_value, default_value)
                        else:
                            deserialize_call = '{} ? {} : {}'.format(
                                input_value, deserialize_call, default_value)

                    self.emit('{}{} = {};'.format(
                        fmt_type(field.data_type),
                        fmt_var(field.name), deserialize_call))

                self.emit()

                deserialized_obj_args = [(fmt_var(f.name), fmt_var(f.name))
                                         for f in struct.all_fields]
                init_call = fmt_func_call(
                    caller=fmt_alloc_call(caller=struct_name),
                    callee=self._cstor_name_from_fields(struct.all_fields),
                    args=fmt_func_args(deserialized_obj_args))
                self.emit('return {};'.format(init_call))

def _generate_description_func(self, data_type_name):
        with self.block_func(
                func='description', args=[], return_type='NSString *'):
            serialize_call = fmt_func_call(
                caller=fmt_serial_class(data_type_name),
                callee='serialize',
                args=fmt_func_args([('valueObj', 'self')]))
            self.emit('return {};'.format(
                fmt_func_call(caller=serialize_call, callee='description')))
        self.emit()

user_args.append((name, typ))
            transport_args.append((name, value))

        with self.block_func(
                func='{}{}'.format(fmt_var(route.name), func_suffix),
                args=fmt_func_args_declaration(user_args),
                return_type='{} *'.format(task_type_name)):
            self.emit('DBRoute *route = {}.{};'.format(
                fmt_route_obj_class(namespace.name),
                fmt_route_var(namespace.name, route.name)))
            if is_union_type(route.arg_data_type):
                self.emit('{} *arg = {};'.format(
                    fmt_class_prefix(route.arg_data_type),
                    fmt_var(route.arg_data_type.name)))
            elif not is_void_type(route.arg_data_type):
                init_call = fmt_func_call(
                    caller=fmt_alloc_call(
                        caller=fmt_class_prefix(route.arg_data_type)),
                    callee=self._cstor_name_from_fields_names(route_args),
                    args=fmt_func_args([(f[0], f[0]) for f in route_args]))
                self.emit('{} *arg = {};'.format(
                    fmt_class_prefix(route.arg_data_type), init_call))
            request_call = fmt_func_call(
                caller='self.client',
                callee='request{}'.format(
                    fmt_camel_upper(route.attrs.get('style'))),
                args=fmt_func_args(transport_args))
            self.emit('return {};'.format(request_call))
        self.emit()

callee=self._cstor_name_from_fields(struct.all_fields),
                    args=fmt_func_args(deserialized_obj_args))
                self.emit('return {};'.format(init_call))

            if not struct.has_enumerated_subtypes():
                emit_struct_deserialize_logic(struct)
            else:
                for tags, subtype in struct.get_all_subtypes_with_tags():
                    assert len(tags) == 1, tags
                    tag = tags[0]

                    base_string = 'if ([valueDict[@".tag"] isEqualToString:@"{}"])'
                    with self.block(base_string.format(tag)):
                        caller = fmt_serial_class(fmt_class_prefix(subtype))
                        args = fmt_func_args([('value', 'valueDict')])
                        deserialize_call = fmt_func_call(
                            caller=caller, callee='deserialize', args=args)
                        self.emit('return {};'.format(deserialize_call))

                self.emit()

                if struct.is_catch_all():
                    emit_struct_deserialize_logic(struct)
                else:
                    description_str = (
                        '[NSString stringWithFormat:@"Tag has an invalid '
                        'value: \\\"%@\\\".", valueDict[@".tag"]]')
                    self._generate_throw_error('InvalidTag', description_str)
        self.emit()

def _generate_description_func(self, data_type_name):
        with self.block_func(
                func='description', args=[], return_type='NSString *'):
            serialize_call = fmt_func_call(
                caller=fmt_serial_class(data_type_name),
                callee='serialize',
                args=fmt_func_args([('valueObj', 'self')]))
            self.emit('return {};'.format(
                fmt_func_call(caller=serialize_call, callee='description')))
        self.emit()

elem_data_type = (data_type.value_data_type if
                is_map_type(data_type) else data_type.data_type)
            serialization_call = self._fmt_serialization_call(
                elem_data_type, 'elem{}'.format(depth), serialize, depth + 1)
            data_struct_block = '^id(id elem{}) {{ return {}; }}'.format(
                depth, serialization_call)
            serializer_args.append(('withBlock', data_struct_block))
        elif is_timestamp_type(data_type):
            serializer_args.append(('value', input_value))
            serializer_args.append(('dateFormat',
                                    '@"{}"'.format(data_type.format)))
        else:
            serializer_args.append(('value', input_value))

        return '{}'.format(
            fmt_func_call(
                caller=fmt_serial_obj(data_type),
                callee=serializer_func,
                args=fmt_func_args(serializer_args)))

pattern = data_type.pattern.encode('unicode_escape').replace(
                    "\"", "\\\"") if data_type.pattern else None
                validator = '{}:{}'.format(
                    fmt_validator(data_type),
                    fmt_func_args([
                        ('minLength', '@({})'.format(data_type.min_length)
                         if data_type.min_length else 'nil'),
                        ('maxLength', '@({})'.format(data_type.max_length)
                         if data_type.max_length else 'nil'),
                        ('pattern', '@"{}"'.format(pattern)
                         if pattern else 'nil'),
                    ]))

        if nullable:
            if validator:
                validator = fmt_func_call(
                    caller='DBStoneValidators', callee=validator)
                validator = fmt_func_call(
                    caller='DBStoneValidators',
                    callee='nullableValidator',
                    args=validator)
        else:
            if validator:
                validator = fmt_func_call(
                    caller='DBStoneValidators', callee=validator)
            else:
                validator = 'nil'
            if not has_default:
                validator = fmt_func_call(
                    caller='DBStoneValidators',
                    callee='nonnullValidator',
                    args=validator)

deprecated = '@{}'.format('YES')
                    else:
                        deprecated = '@{}'.format('NO')

                    if not is_void_type(route.result_data_type):
                        caller = fmt_class_type(
                            route.result_data_type, suppress_ptr=True)
                        result_type = fmt_func_call(
                            caller=caller, callee='class')
                    else:
                        result_type = 'nil'

                    if not is_void_type(route.error_data_type):
                        caller = fmt_class_type(
                            route.error_data_type, suppress_ptr=True)
                        error_type = fmt_func_call(
                            caller=caller, callee='class')
                    else:
                        error_type = 'nil'

                    if is_list_type(route.arg_data_type) or is_map_type(route.arg_data_type):
                        dataStructSerialBlock = '^id(id dataStruct) {{ return {}; }}'.format(
                            self._fmt_serialization_call(
                                route.result_data_type, 'dataStruct', True))
                    else:
                        dataStructSerialBlock = 'nil'

                    if is_list_type(route.result_data_type) or is_map_type(route.result_data_type):
                        dataStructDeserialBlock = '^id(id dataStruct) {{ return {}; }}'.format(
                            self._fmt_serialization_call(
                                route.result_data_type, 'dataStruct', False))
                    else: