'We dynamically generate this, since we want it the expiration clock to
start when the message is created, not when the record is created.
Arguments:
name (str): Name of the image (e.g. "photo_id" or "face")
Keyword Arguments:
override_receipt_id (str): If provided, use this receipt ID instead
of the ID for this attempt.  This is useful for reverification
where we need to construct a URL to a previously-submitted
photo ID image.
Returns:
string: The expiring URL for the image.'

def image_url(self, name, override_receipt_id=None):

    path = self._get_path(name, override_receipt_id=override_receipt_id)
    return self._storage.url(path)
