'Returns the path to a resource with this instance\'s `receipt_id`.
If `override_receipt_id` is given, the path to that resource will be
retrieved instead. This allows us to retrieve images submitted in
previous attempts (used for reverification, where we send a new face
photo with the same photo ID from a previous attempt).'

def _get_path(self, prefix, override_receipt_id=None):

    receipt_id = (self.receipt_id if (override_receipt_id is None) else override_receipt_id)
    return os.path.join(prefix, receipt_id)
