def cancel_signature_request(self, signature_request_id):
request = self._get_request()<EOL>request.post(url=self.SIGNATURE_REQUEST_CANCEL_URL + signature_request_id, get_json=False)<EOL>
Cancels a SignatureRequest

        Cancels a SignatureRequest. After canceling, no one will be able to sign
        or access the SignatureRequest or its documents. Only the requester can
        cancel and only before everyone has signed.

        Args:

            signing_request_id (str): The id of the signature request to cancel

        Returns:
            None