code: def sign(self, msg, key):
          
  
          if not isinstance(key, ec.EllipticCurvePrivateKey):
              raise TypeError(
                  "The private key must be an instance of "
                  "ec.EllipticCurvePrivateKey")
  
          self._cross_check(key.public_key())
          num_bits = key.curve.key_size
          num_bytes = (num_bits + 7) // 8
          asn1sig = key.sign(msg, ec.ECDSA(self.hash_algorithm()))
          # Cryptography returns ASN.1-encoded signature data; decode as JWS
          # uses raw signatures (r||s)
          (r, s) = decode_dss_signature(asn1sig)
          return int_to_bytes(r, num_bytes) + int_to_bytes(s, num_bytes)
docs: Create a signature over a message as defined in RFC7515 using an
          Elliptic curve key
  
          :param msg: The message
          :param key: An ec.EllipticCurvePrivateKey instance
          :return: