code: def should_check_ciphersuites(self):
          
          if isinstance(self.mykey, PrivKeyRSA):
              kx = "RSA"
          elif isinstance(self.mykey, PrivKeyECDSA):
              kx = "ECDSA"
          if get_usable_ciphersuites(self.cur_pkt.ciphers, kx):
              return
          raise self.NO_USABLE_CIPHERSUITE()
docs: We extract cipher suites candidates from the client's proposition.