def create_id(self, prefix="guid"):
        """Create an ID.

        Note that if `prefix` is not provided, it will be `guid`, even if the
        `method` is `METHOD_INT`.
        """
        if self.method == IDGenerator.METHOD_UUID:
            id_ = str(uuid.uuid4())
        elif self.method == IDGenerator.METHOD_INT:
            id_ = self.next_int
            self.next_int += 1
        else:
            raise InvalidMethodError(self.method)

        return "%s:%s-%s" % (self.namespace.prefix, prefix, id_)
Create an ID.

        Note that if `prefix` is not provided, it will be `guid`, even if the
        `method` is `METHOD_INT`.