How to use the fastly.models.Service function in fastly

if item_value is not None:
            return DictionaryItem.upsert(self.conn, {
                'service_id': self.attrs['service_id'],
                'dictionary_id': self.attrs['id'],
                'item_key': item_key,
                'item_value': item_value,
            })
        return DictionaryItem.find(self.conn, service_id=self.attrs['service_id'], dictionary_id=self.attrs['id'], item_key=item_key)

    def items(self):
        return DictionaryItem.list(self.conn, service_id=self.attrs['service_id'], dictionary_id=self.attrs['id'])

class DictionaryItem(Model):
    COLLECTION_PATTERN = Service.COLLECTION_PATTERN + '/$service_id/dictionary/$dictionary_id/items'
    INSTANCE_PATTERN = Service.COLLECTION_PATTERN + '/$service_id/dictionary/$dictionary_id/item/$item_key'
    INSTANCE_CREATE_PATTERN = Service.COLLECTION_PATTERN + '/$service_id/dictionary/$dictionary_id/item'

    @classmethod
    def upsert(cls, conn, data):
        # https://docs.fastly.com/api/config#dictionary_item_34c884a7cdce84dfcfd38dac7a0b5bb0
        instance = cls.construct_instance(data)
        instance.conn = conn
        params_str = urlencode(instance.attrs)
        resp, data = instance._query('PUT', body=params_str)
        instance._original_attrs = data
        instance.attrs = data
        return instance

    def _collection_query(self, method, suffix='', body=None):
        # DictionaryItem's create API URL is inconsistent with the other APIs,
        # with the use of singular and plural ("item" and "items").
        # Only use case for POST on this Model is to create one item, so swap in that API URL.

def service(self, id):
        return Service.find(self.conn, id=id)

def services(self):
        return Service.list(self.conn)