def __call__(url=None, data={}, headers={}, cookies={}, **kwargs):
    """Start a Celery task that will execute a post request.

        The optional `url` argument may be used to override `self.url`.
        The optional `data`, `headers` and `cookies` args will update
        the corresponding self.* attributes.

        `self.task.apply_async` will be called
        and is expected to call `url` with
        `self.headers` as request headers,
        `self.cookie` as request cookies, and `self.data` as post data
        via the python request library.

        `**kwargs` will be passed through as arguments to celery
        `apply_async` so you can set async execution options like
        `countdown`, `expires` or `eta`.

        All arguments should be immutables that can be serialized.
        """
