Add a :class:`Task` to the current :class:`UserStory` and return it.
        :param subject: subject of the :class:`Task`
        :param status: status of the :class:`Task`
        :param attrs: optional attributes for :class:`Task`

def add_task(self, subject, status, **attrs):
        """
        Add a :class:`Task` to the current :class:`UserStory` and return it.
        :param subject: subject of the :class:`Task`
        :param status: status of the :class:`Task`
        :param attrs: optional attributes for :class:`Task`

        """
        return Tasks(self.requester).create(
            self.project, subject, status,
            user_story=self.id, **attrs
        )